Recently one of our readers asked us to post an article about the benefits of Windows driven VPS hosting. Since we’ve been looking into provision of this service as well, there was some interesting information gathered and we would like to share this with you. We thought that showing both upsides and downsides of this type of hosting is more fair. Sure, this article is posted from our point of view, so it reviews peculiarities of Windows hosting in terms of use of VPS-hosting specifically as a platform.

How is Windows run on VPS servers?

Running Windows on VPS usually implies the use of two types of virtualization technologies – XEN – the technology, generally applied in creation of fully virtualized VPS platforms and Hyper-V – special virtualization system, developed by Microsoft to run Windows VPS server only. XEN is known to many of our readers – this virtualization technology allows to create and manage virtual servers keeping them completely isolated from each other, while using same hardware resources by different system kernels – each fully virtualized environment keeps the system with its kernel that addresses to the layer of virtualized hardware.

As for Hyper-V – this technology needs some description. In fact, it is a hypervisor that works on the basis of partitioning with at least one parent partition that has access to hardware and can create child partitions that host guest OSs within virtual environment – just like XEN and its interfaces. But if you take a closer look, you can see that Hyper-V is a version of core installation of Windows Server 2008 with virtualization support – which makes it look much like OpenVZ that utilizes modified Linux kernel. Thus, it is fair to call it a symbiosis of two technologies.

What is so special about Windows VPS Hosting?

VPS as a platform to run Windows on has become a real discovery for many users who needed Windows-based hosting but could hardly afford a dedicated server while experiencing issues with shared hosting, run under this OS. Indeed, using Windows as a server OS and namely for hosting needs is quite troublesome – initial resource usage is higher than that under Linux, disk usage policy and work of the disk subsystem is more complex, and full functional access can be achieved only by establishment of remote desktop connection (RDP) or a control panel. The latter aspect caused the biggest inconvenience, since shared hosting users are not usually provided with RDP access while the control panel functionality is limited so, that the lack of privileges makes the use of many tools impossible.

Use of VPS hosting has solved many of those problems – VPS carriers with large amounts of RAM allowed to delegate resources that are enough for the system to operate with additional software and cover the loads created by resource intensive programs (e.g. Microsoft Exchange server); RAID hard disk arrays + virtual disk partitioning allowed to minimize the I/O loads and increase the read/writing speed. Finally, a VPS allowed to create isolated environment, which enabled the users to manage their servers under “Administrator” privileges.

What are the downsides to keep in mind?

Besides the obvious upsides of Windows-based VPS hosting, there are, however, downsides that should be considered while making the choice. First of all the price – when it comes to evaluation of Windows hosting in general and its hosting on a standalone server in particular, all licenses, starting from the OS itself and all software, seem to cost an arm and a leg. The server is not going to be cheap as well – as mentioned above, Windows requires more resources, so the least powerful virtual server you will need is a XEN-based VPS – which are more expensive than those under OpenVZ – with 1 GB of RAM at minimum (you can find plans with 512 MB of RAM offered, but there won’t be much resources left to operate with). A Hyper-V based server with same resource rates will grant you more stable hosting, but it is going to cost more.

Mentioning this downside we don’t mean that the pricing difference is going to reflect in tens of dollars compared to Linux VPS hosting, but this may make some users think, whether they need it – at least those, who are not sure, if they are going to prefer ASP and .NET to PHP. If you are sure about the use of Microsoft software, here are some more tips on what you should be careful about.

Accessibility. You may be happy about having RDP and control panel access to your server – both provide clear intuitive interfaces, the former actually makes you feel like sitting at your home desktop, but are those means actually enough? If your server gets too overloaded, you may not be able to access it to reboot it, so you will need to send a support request which definitely causes a time loss. What you may make sure about before choosing your Windows-driven VPS host, is if they offer remote reboots from the host’s client panel – this may save your time.

Monitoring. Unlike Linux-based VPS servers, those running Windows need more severe monitoring, which may result into either bigger expenses – so you will need to hire an administrator or involve your host’s support team – or stresses, caused by constant inspection of your server’s state and investigation of issues it has or may have in future.

There are even more aspects, related to OS Windows itself to be kept in mind – security, as Windows is quite vulnerable; software-related; usability-related and others. So it is fair to get back to the question, whether you really need it. Many webmasters who are asked to create a site to work on a Windows server usually ask this question. And when they receive a solid “yes” they want the project to be described as clearly as possible. Thus, if you imagine your project well and see the full picture of how it is going to be run and why exactly it needs Windows, you are on the right way, and we hope, that your experience in this is going to be positive.

This question is the one many people ask themselves before purchasing their first VPS. Indeed, when you only check out the plans, you cannot tell for sure what intensity of RAM usage you expect. What you know, is the approximate amount of physical memory used by the software you are going to run on your VPS. Software system requirements, however, are usually not enough to estimate the real use of RAM needed for the particular application or script to operate, and thus it is hard to know how much physical memory the entire server with all its background processes in general is going to need.

There are some facts that you know that might help you there. For instance, we know that the server in its basic installation – usually LAMP – requires at least 128 MB of RAM. Choice of the control panel will make you add another 64 MB to your requirements (if your choose WebMin or DirectAdmin) or even 128 MB – if you want to run cPanel. This makes a minimum of 256 MB with a lack of operating options. What you can run there is email and FTP exchange (not intensive though) and hosting of simple websites. Dynamic and script-driven websites, such as CMS will also fit this configuration but you may need to implement many adjustments, some of which can limit the functionality of your online project.

If you look into running something more serious on the Web, you will need to search for a more solid solution. Let us review bigger VPS configurations and estimate what can be hosted there.

512 MB

This is one of the most popular configurations available on the market of VPS hosting. A VPS with 512 MB of RAM usually becomes a step-up for users who have never dealt with VPS servers before and who gave this type service a try on a smaller plan and then requested an upgrade.

If you want to host E-commerce software or run a script that is going to use your server resources constantly – a VPS with 512 MB of RAM is going to suit you perfectly. This plan will also fit those, who look into using a VPS as a platform for hosting reselling – simple shared hosting, of course. WordPress and Magento users will also find such a VPS a better luck, since 256 MB virtual machines never let them run those CMS full-throttle.

1024 MB

A one-Gig VPS is a choice of a Pro. Many gurus and experienced webmasters, as well as resellers and other online business holders, either purchase those servers at once or upgrade to them shortly.

If you deal with hosting reselling, you will find a VPS with 1024 MB RAM to be a perfect solution for serious reseller business. Unlike smaller VPS plans, those and higher let you offer the so-called Master reseller hosting which implies that your resellers will be able to sell hosting, too. And of course, a more powerful VPS will let you manage the clients easier. Indeed, if you have a thousand clients or more, whatever the business you do is, why should you partition them into groups to send emails hourly so as not to overload the server. You deal with e-commerce, so you must have some special offers and discounts and you want to be sure, everyone knows it – a powerful VPS will let you notify everyone at once without overloads or any other issues.

2048 MB

If you need a power of a dedicated server, but do not want to pay extra for the features you do not need, a 2 GB VPS is something you will like.

Those servers are usually the top ones among many VPS hosting providers and thus have the highest privileges on the carrier. This feature will make you feel absolutely comfortably on your VPS and it is worth it. Such a powerful VPS is heaven for big online projects and geeky things – those servers are capable of letting you refuse from standard server configuration, so one can easily install there such popular software as Java, Tomcat webserver, FFMPEG and many other tools, to make their online project a hi-tech multimedia pad.

We hope that this review of the most popular VPS plans helped you find out what you need or may need for your online business. If it did, you may like the news that since recently we run a special offer that has doubled RAM on all our VPS servers, so now our 256 MB, 512 MB and 1024 MB plans come with 512, 1024 and 2048 Megabytes of RAM accordingly.

After we have delivered you numerous articles on different aspects of VPS hosting, we’ve noticed that we need to get back to this topic again. Once again we are going to talk about the problem of choice of a VPS server. This time we are going to take a look at this question under a different angle – let us share some interesting tips on how to tell if what you see when checking out the feature/pricing page of your potential VPS host is what you are going to get. While introducing you choice-making tips in our previous articles we usually referred to the technical aspect of VPS hosting, today we are going to analyze the VPS hosting from the point of view of a customer.

How much RAM do you get in fact?

When you see a 1 GB VPS plan at a very low cost, don’t be too fast in making optimistic conclusions. Check if this entire amount is guaranteed RAM. The best option is to contact sales support – then you are going to have a proof – a copy of your chat or email. But if you don’t have time for those checks, there is a quick way to find it out on your own – check the virtualization type used by this host. If it is XEN – be sure the entire 1 GB of RAM is guaranteed. If they use OpenVZ (the hosts that use it often say their VPSes are powered by Virtuozzo), there’s a risk, that their pricing provides the combined amount of RAM – guaranteed + burstable (RAM, that may be allocated only for a short period of time and thus – not constantly available). Since RAM is the main feature of any VPS server, this should one of the first points you verify before moving any further.

CPU units

Checking out pricing of some VPS hosts, one can find such feature as CPU units. This parameter shows the CPU frequency, available for the given VPS. Although it looks rather informative and lets the potential client compare the offered plans in more details, it’s not quite a correct way to represent VPS CPU specifications. To find out how powerful the CPU of the given VPS is, you need to know, what number of cores the entire VPS-carrier has, what their frequency is and how much of this power is delegated to the specific virtual machine – the latter factor depends on performance priority.

If you don’t know, how to interpret this information, you can simply ignore it. If you do need the details, you can have a brief consultation with the sales department of your potential host. This will let you find out the specifications of the carrier. The more powerful it is and the bigger the plan you are looking into, the more powerful your VPS is going to be.

Disk Space

Since VPS servers are usually offered as a fast solution that is cheaper than a dedicated server, those are not designed for large data processing. The minimal plan at some VPS hosts may offer as little as 10 GB of disk space. If you are going to host a few web pages, it’s alright, but if you work with email and databases, you need to consider disk space allocation rather carefully. Now let us count what you have in the end – after your server is setup, the system may take up to 2 GB of disk space. Any backup you make is going to create a file of the size approximately equal to the size of your /home directory. Not that much space left, isn’t it? That is why another Gigabyte of your virtual HDD may become vital. Well, it can also be taken by swap. According to the architecture of OS Linux, swap is a fixed disk partition, not a file, unlike on Windows – therefore, before you order a XEN-based VPS, you need to consult sales department first, to find out whether /swap is counted with the disk space offered or not.

Summary

If you want to be completely sure about your future VPS host, you need to find out as many details as you can before you actually sign-up for their services. Your potential host may not list everything on their web-page, it’s alright, but their sales and technical team should always be able to explain these or those aspects of hosting with their company. If it happens that some of your questions remains unanswered, you have serious reasons to not consider this host. If you are looking for an affordable and reliable VPS host right now, please spend another minute checking out our plans here at SiteValley.com.

A week ago Ubuntu Mini Remix announced their new release of Ubuntu 10.10 livecd.  That’s the fourth release of Ubuntu with minimal software set delivered by UMR, who seem to think different of this operating system. Those who consider Ubuntu to be an OS-in-a-box will be surprised by simplicity of its minimized installation medium. But will they actually like it?

We would have never intended to discuss that if we hadn’t installed an Ubuntu-based VPS recently. We at Sitevalley.com do not receive such orders frequently – installing Ubuntu on the server requires many tweaks and disables the use of automating control panels, such as DirectAdmin or cPanel, which means more manual technical work for the customer. Generally, Ubuntu is not actually a true server distro – this OS is known as a perfect desktop solution – however, if the user is good at a certain OS specifically, it’s reasonable to let them work with it…

This very question of reasonability has actually fired up a discussion on whether Ubuntu Mini is going to be in demand. The ideas below are summary of this discussion that we are going to share with you.

The Idea of UMR

If you take a look at the current Ubuntu community and the way they work – you will see that the “OS-in-a-box” idea was developed into generation of multiple releases with a wide range of tweaks and customizations that are called derivatives. Apart from releases for servers and desktops (as well as different desktop managers) Ubuntu now offers specially optimized versions for Cloud computing, netbooks, Christians and Muslims and different activities (e.g. for multimedia creation or education). There are many more derivatives, you can find here, but even those above make think that Ubuntu has covered all possible spheres of users’ origin (there are many fully localized versions), interests and activities. This in turn emerges a question – what else may one need?

No matter what may be needed, there’s another question to rise – do you really need all those preinstalled applications? And here appears UMR as an argument for a negative response. So, if it’s a “No” and you don’t need any of those preinstalled solutions – you are ready to get acquainted with Ubuntu Mini. But what is this OS actually like?

Before UMR many people who needed simplified distros used to refer to more experienced Ubuntu users and enthusiasts who created LiveCDs for them. Some even used server installation media or burned their own installation CDs. Releases, provided by Ubuntu Mini are close to Ubuntu Desktop, they are, however not overstuffed with software and applications one may not need and thus are more flexible and customizable. It is obvious that the main idea of the UMR project is simplicity – this derivative is for everyone who likes Ubuntu and wants to run it their way and with no pain in their necks.

Who Is Going to Use UMR

Such releases as Ubnutu Mini are usually called geeky. We are not sure you’ll find many Ubuntu users, who’d like to switch to something self-compiled that may corrupt due to incompatibilities or after an unsuccessful update or something like that. A Mini may however interest those, who deal with old or peculiar hardware or need to run some specific software or a fixed set of applications. UMR product can also be used for creation of a custom Ubuntu build – you may boot a Mini, install all the needed software and customize it and then burn it back to another CD/DVD to keep it near at hand – this solution works perfect if you need to setup a specifically configured OS on several machines or simply want to avoid headaches, brought by OS reinstallation.

This flexibility is something to pay attention to and the fact that Ubuntu Mini is still Ubuntu may really make UMR very popular. Not many Ubuntu users would like to switch to other distros just to get a flexible customizable OS. Although such distros as Gentoo, Fedora or Debian – a distro, Ubuntu has actually derived from – may be perfectly used for both desktops and servers, Ubuntu still remains the simplest OS.

Conclusion

If you need a Linux distro which is easy to install and operate and which is customizable enough to compile it in the very way you need – you should have a look at Ubuntu Mini. If you find Gentoo or Debian complicated to work with but require the same simplicity of the installation medium – you should give UMR a try. Finally, if you are new to Linux and want to get acquainted with it quickly and with manual efforts for better understanding – go to Ubuntu Mini Remix website and download it.

If you have some interesting facts about Ubuntu to share or want to take part in the discussion of UMR usability, feel free to join us on Facebook.

Starting reseller business five years ago or earlier the business owner had only two options: signup for a shared hosting account with reselling feature or order a dedicated server. The initial option was a fine solution for starters since it was cheap, but as soon as the resellers’ business developed they needed a step-up. The problem however was that a dedicated server was still not affordable for them, while the resource usage of both resellers’ and their resold accounts became completely unbearable for a standard shared servers. This led to continuous suspensions of accounts and constant quarrels, some of which were even brought to social media. Finally, either the hosting company met halfway with the reseller offering some discount on upgrade or the reseller quit the company to signup for another shared hosting plan with another host. A lot has changed since VPS hosting has been introduced, so nowadays hosting reselling is not that tough, expensive and risky business.

What is a VPS and How It Works?

A VPS is a Virtual Private Server – an isolated virtualized environment with its own OS (Operating System) and emulated hardware, hosted on a physical server a.k.a. carrier. Those virtual servers are setup within a carrier by means of virtualization technology, which allows to run several isolated boxes, letting them operate independently from each other and provide the performance rates, similar to the ones of a dedicated server. Though there are several virtualization technologies, the common idea implied in all of them is to create conditions, on which several operating systems could function within single hardware set – one physical machine. There are many backgrounds for such an idea – energy use reduction, hardware use optimization, setup and maintenance cost cutting, etc. The main thing is that this idea works well for many business solutions including hosting reselling – let’s take a closer look, at which aspects specifically.

Reasonable Price

An upgrade from a shared reseller plan to a VPS or initial start of reseller business on a virtual server is quite an affordable solution, since it sets the business owners free from enormous expenses of hosting. Resellers can then invest their money into SEO and social media marketing to have their business promoted on the World Wide Web. Apart from just being a good fund saving solution, a VPS stimulates the reseller to fair pricing formation. This is one of the key points in this business, since, on the one hand, there are too many competitors, while on the other hand – spending much money on expensive hosting may force the reseller to set high prices, too high prices for the provided services.

Smooth Upgrades

Taking into account the further growth of their business, resellers may need the further upgrade of their VPS. The virtualization technology allows performing such upgrades staying on the same server, by just increasing the resource usage quotas – to some extent of course. Thus, since VPS hosting providers usually offer 3-5 different plans, a reseller may have his or her virtual machine upgraded to a couple of levels higher. Such upgrades are very convenient as long as they cause no downtime, which is critical for resellers and their clients.

Master Reselling

The feature of master reseller plans provision – plans which allow reseller’s customers to resell hosting, too – was usually available for the dedicated server users only. Modern technology allows to offer such plans on a VPS. Of course, this solution requires a more powerful VPS, but the fact is that resellers can now provide reseller hosting on their own with less expenses involved.

Virtual Hardware Makes No Real Issues

One of the main benefits of VPS hosting is the absence of hardware issues. This point is the most essential for resellers. If the hosting reselling business owner is using a shared server and this server crashes, a reseller depends on his/her hosting provider, who in turn depends on datacenter staff. As far as such issues may take long to get resolved, a terrific waste of time may cause resellers to lose their customers. If it is a dedicated server, the issue may take less time but more money (e.g. if there’s no SLA guarantee, if the server is purchased from the datacenter directly, etc.). Being hosted on a VPS a reseller is set free from any possible hardware issues, except for those which may happen to the carrier. In this case, however a Virtual Machine can be cloned and moved and then started on the backup server.

Server Management

Performance is not the only feature of the VPS, which makes it look similar to a dedicated server. Another feature is management. Administration of the server does take much time. If there are a couple of dozens accounts hosted there, administration and management of such a server may become a nightmare. Those who were using a shared reseller hosting account can tell how exhaustive it can be – to just manage clients’ accounts and billing. Imagine what it would be if they also had to administrate the server itself. Well, you may not imagine this – virtual servers are administrated by the host’s technical staff.

Another positive thing about VPS management is the client side. Let us refer to shared reseller hosting users again – I believe all of them can confirm they had a situation, when they requested assistance for their customers, even on their behalf and received a deny. This may sound fair enough from the host’s side in terms of support provision policies or taking the fact the server is shared and is used by many other people and so on, but the problem remains and the reseller’s client stays unsatisfied. Use of a VPS helps to resolve such issues quite well. First of all, a VPS is one of the top products at many companies; therefore its support is privileged. Another point is server isolation – it allows the host’s support team to modify initial server configuration and apply non-standard solutions. As a result – the reseller can take care of many other things important for his or her business.

Customizability

Another advantage of a Virtual Private Server for a reseller is the ability to customize it. The isolatability of the VPS and the presence of root access to it allow the reseller to tune-up and reconfigure different services, what helps minimizing load and cut server resource usage. Considering the constant lack of disk space and taking into account active file transfer and mail exchange, such option may do much good to both reseller and all his or her clients, since a couple of resource intensive accounts may make other account owners and the entire VPS experience services slowdown and even overload. For instance, a reseller may limit the number of FTP and SMTP/IMAP connections to the server to lessen the number of request and the load on those services, in turn. Furthermore, the administrator of the VPS may simply disable IMAP protocol on the server, so that all the users could use only POP3, which implies the download of all messages to the local computer of the user. Such limitation helps saving server space and gives the reseller a ticket to overselling.

Overselling

Overselling is actually not the best strategy, but many hosting business owners apply it while creating their hosting packages and setting prices for provided services. In a nut-shell, this strategy means offering and selling more, than one really has. This mostly concerns disk space and bandwidth quotas, but hosting sellers and resellers usually oversell on more services – number of virtual hosts (addon and subdomains), email and FTP-accounts number, size and number of the databases allowed under a single account. Though overselling strategy does not always bring many problems, the risk of slowdowns and overloads may grow with its use. Thus, if the hosting business owner considers this solution important for his/her business, overselling may be applied. The reseller however should make sure the server in use is capable of carrying out such loads.

Modularity

The problem of load and its reduction has always been in question for all server administrators. Even for those who use their server resources rationally. The solution to this problem was found since the load balancing technology had been invented. This technology requires the use of several servers – each of them is processing requests addressed to a service or a set of services specifically configured on this standalone machine. Load balancing may look an expensive solution, but its price is justified by the positive effect it makes. Additionally, talking about separate machine for service processing, we mean virtual machines, too. Those are significantly cheaper, as far as you know, so let us see how resellers can have load balancing applied in their business.

Imagine you have a top VPS. To make the story more interesting, imagine that you oversell and already have about 50 clients. You start experiencing load issues because some host over 20 domains; some use your service as a small email server and some organize file sharing over FTP. Such load is bearable yet, but you realize that the further growth of your business may require an upgrade – this time to a dedicated server. You are definitely not interested in wasting time on transfers, DNS-rearrangement and other related problems. Thus, you get a couple of simplest cheaper virtual servers, one of which is let’s say set to process MySQL requests, while another deals with mail exchange. Even such move is going to seriously lessen the load on your VPS.

Summary

The development of the reseller’s business may later require an upgrade to a more serious solution – to a dedicated server. A finely tuned VPS however can let a reseller host his resold accounts for a long time with no issues and for a significantly affordable price. If you are not sure about what hosting plan to choose to start your reseller campaign – order a VPS and start seizing the market of web hosting.

Choosing The Right Solution. Image source: planetgreen.discovery.com

Last time we spoke about making a choice of a Virtual Private Server in terms of the configuration varieties. Today we are going to continue our research and tell some useful facts about types of websites, applications and services one may use on a VPS and the related dependencies.

There are many types of websites and online services on the Internet that differ by system requirements, performance or way of work. Sure, most websites work with a standard configuration and software set but some websites and especially services need an accurate configuration pick and fine software tune up. In this regard we are going to list the most popular services and applications in the today use and find a correspondent VPS-based solution for each. Well, let’s start.

1. Email and ftp transfer services

Email and FTP transfer

VPSes are widely used for establishment of certain separate services on them. If you want to get a simple email or ftp server which would need no constant web-access, you may get the simplest custom configuration of your virtual server, which would include just the OS and basic mail exchange/file transfer services. If you wish to run some additional scripts, you have LAMP installed as well (you will anyway need Apache in order to provide webmail access or check the uploaded files via web). In such cases the control panel is not essential (some users do not even include it to their orders) what makes the choice of the OS not crucial as well. Neither is the choice of the virtualization type. Such web-inactive resources do not usually require severe monitoring or many maintenance efforts, especially when strict connection quotas and transfer rate limits are set. CPU/RAM parameters may also be minimal, however those exactly parameters will let you define, which limits to set.

2. Simple static websites hosting

Simple website. Image source: techpin.com

If you have a simple website, which hosts static unchanged content and which is not frequently updated – a minimal VPS configuration is what you need. Depending on the visitor rate and activity of other servers (email exchange, ftp transfers, MySQL requests), you may choose one of the following options: 1) simplified maintenance and normal performance or 2) higher performance with less convenient maintenance

Choosing the first option you are likely to signup for a cPanel-based VPS with CentOS installed on it. While other control panels tend to be less resource intensive, cPanel/WHM provides you with ultimate maintenance and adjustment options, although this is going to cost you more RAM. Thus, you should choose a VPS with 512 MB of RAM. Such amount may look more than you actually need, but on the other hand it will provide you with reserve physical memory, needed for further growth of your project. Xen is more recommended, but OpenVZ virtualization may be used for cost cutting.

The second option is to provide higher performance rate for a lower price. This may somehow decrease the server management convenience level, but if you are good at basics of non-interface server administration you are not supposed to experience many issues. Your VPS will have no control panel or the least resource hungry one (WebMin or DirectAdmin) and will be able to run a “lighter” OS – FreeBSD. To gain more performance you may refuse from Apache (the LAMP classics) and have Nginx or LightHTTPD installed. Finally, you can choose the cheapest XEN VPS with 256MB on a board for the utmost productivity rate – XEN is more recommended for such configuration, since the more manual tune up you are going to bring in, the more you will feel the need of a fully virtualized server.

3. Hosting of dynamic and script-built websites

Script-built website code. Image source: blog.ning.com

Such websites as forums, blogs and online-stores are not those to spare money on – especially, if you use them for your business. Therefore you should look into the most stable configuration, which almost entirely excludes self-management (unless you or your web designer is familiar with server administration). The use of FreeBSD becomes questionable as well – this OS does require more experience of work with *NIX. As for the control panel – you are still able to choose between two of them – cPanel or DirectAdmin since both usually come with automatic script installers. LAMP set is not to be changed or tuned since any website software requires otherwise. The most serious question however is the virtualization type. The first thing to make sure about before selecting one is the completeness of your project: if the project is being tested or developed or simply going to keep growing – you should choose OpenVZ. This virtualization technology will be reacting smoother to all the changes, including load spikes and temporary memory overuse. If your project is final and the only thing to modify is the content – you can choose a XEN. On conditions, that no configuration changes are going to be made, such VPS can show you surprising performance. Recommended minimal RAM amount is 512 MB.

4. Default Resource Intensive Software

Resource Intensity. Image source: freeinfosociety.com

Among the script-built websites there are those, which software is resource intensive by default. Such scripts as Drupal or WordPress (especially enhanced with some plug-ins or add-ons) or any intranet or social networking software have high system requirements and need much server tune-up to be performed. Thus, the refuse of LAMP is the first step, very frequently offered by the webmasters. It is not even actually a refuse, though an enhancement, since Apache keeps working as a backend web server, while Nginx or LightHTTPD serves as a frontend. Since cPanel/WHM can provide the utmost maintenance and management option, it usually becomes a sole choice, which in turn emerges the choice of CentOS as the operating system. The most recommended virtualization type is OpenVZ since the temporary overload and memory overuse are much likely to be expected. The hardware configuration is 1024MB and higher. If you manage to find a 2GB RAM supplied VPS – you may think about XEN. Still, you should think twice.

5. Hosting Reselling on VPS

Reseller Business. Image source: flickr.com

Hosting reselling is one of the most popular online businesses, while VPS is the most popular way of its realization. Shared reseller servers can hardly provide the needed performance; additionally the limitations of the hosting provider may confuse a reseller and make him give up some of his or her ideas. A VPS offers perfect conditions for reselling – those however should be used wisely. If there is a choice the OS, the software set needs to be standard and not tuned. The control panel must be present on any conditions; it should be user friendly and intuitive enough, therefore the most recommended options are cPanel and DirectAdmin. Virtualization type does not matter much, but if you oversell it is recommended to choose OpenVZ. Minimal RAM amount is 512MB (regardless of the control panel type).

The Bottom Line

When we released the first part of our research, it was not as detailed as it should be to get a full picture. Now we can say that the analysis of particular website and service types might be more helpful for those, who consider a VPS as a hosting solution but are not yet sure about the preferred configuration. If you have more examples of VPS hosting usage or want to share what you or your friends host on a virtual private server – don’t hesitate to leave your comments or take part in a discussion at our Facebook page.

If you have already made up your mind regarding the VPS configuration you would like to have, take a look at the VPS plans we offer at SiteValley.com. The variety of virtualization types and control panels, flexible prices and friendly support – that’s what you are going to get there.

Choosing The Right Way. Source: thefrisky.com

When website owners decide to purchase a Virtual Private Server for their websites, they are often concerned about its configuration. If upgrading from a shared hosting account, a user may pick a too weak server and put it down right after the website launch, as virtual servers do not have such strict limits on resource usage set, as shared ones do.

If someone is purchasing a VPS at once, without having the site actually tested elsewhere before, its owner may pick a wrong software configuration and not even have the website started (we don’t think that error pages hosting is funny or profitable).

A fair question is “Which VPS configuration to choose to provide my website with the most optimal hosting solution?” Here go the answers.

VPS Configuration Types

Virtual private servers differ in their configuration by many parameters. Those usually depend on their vendors’ likes and commercial interests; presence of trained personal, able to work with this or that software; welfare and funding, etc. Studying the market of VPSes we can define the following main configuration options:

1. Virtualization Type

Virtualization Technology. Source: ibm.com

Nowadays there are two most popular virtualization technologies – Xen and OpenVZ. We have already talked about both and compared them, so to make the long story short, we are just going to tell, that Xen technology supports full virtualization and a wide range of operating systems. It does not have any inter-carrier shared resources, what makes the work of each server autonomous (there is even a separate /swap partition created under each virtual machine). OpenVZ is a specialized Linux-solution, which is faster but it lets the carrier share resources (RAM/CPU), what may cause overload issues to both virtual and physical machines. On the other hand, resource sharing allows OpenVZ users to get temporary RAM-boost – so-called burst-RAM.

2. Control Panels

Most Popular control panels

When one speaks about comfortable and user-friendly hosting, they first of all mean the control panel. A control panel is very important for site management, so it’s easy to imagine how essential it is for administration of the entire server. VPS vendors usually provide control panels on a partnership basis or as license resellers. This allows them to both get licenses at lower cost and provide control panels either for free along with the VPS’s or for a significantly smaller price. Leading VPS control panels are DirectAdmin and cPanel. cPanel has a VPS-optimized build which may be a perfect solution for those, who strive for automation. There is one more panel, frequently offered by VPS vendors – Webmin – free open source server/account management software.

NOTE: cPanel is a resource intensive panel compared to Webmin or DirectAdmin. The former requires 256 MB RAM for full functionality, while the latter ones – only 64 MB.

3. Installation of Basic Services

Linux-Apache-MySQL-PHP. Source: graphicsyork.com

The generally installed software-bind is known as LAMP – Linux + Apache + PHP + MySQL. This configuration works well with any kind of sites and is recommended for use. Some scripts and serious web-projects, however, require different pieces of software. The most frequently substituted element is Apache – the webserver. Users install LightHTTPD or Nginx instead, to improve the web-content processing speed. It is a known trick, so many VPS vendors offer either blank servers (without software and sometimes even the OS preinstalled) or custom software set installation.

NOTE: LAMP is the most recommended software set for cPanel-based servers, as cPanel allows to manage all services via web-interface.

4. Operating Systems

Linux and FreeBSD. Source: linuxwallpaper.net

One of the best Linux distros, which has proved its reliability is CentOS, so no wonders it is one of the most frequently setup default OS, provided on VPSes all over the market. The vendors, however understand that the users are interested in customization, so they offer other distors, too. The most popular are Ubuntu, Fedora and Gentoo. Additionally, many offer FreeBSD (Unix).

NOTE: Though FreeBSD is faster in some extent, it is not recommended for use with cPanel, as far as FreeBSD may start malfunctioning after automatic cPanel update.

5. Amount of RAM and Disk Space

Piece of Hardware. Source: fuhrmann-itservice.de

Those parameters are usually set according to the carrier server specifications. Before the VPS hosting plans are created and approved, the marketers study the demand for this or that plan type (usually studying competitors’ plans with more or less similar quotas) and their actual relevancy (e.g. instead of buying some top VPS plan it may sometimes be more desired to get a dedicated server for almost the same amount). So far the most popular RAM quotas are: 256, 512 and 1024 MB. The disk quota has more floating values, the minimal is usually 20 GB, while the maximal may vary from 80 GB to 120 GB

Matching The Details

Say, you have picked a host you would like to get a VPS from. You studied the plans they offer and their pricing seems to look good. Before you make your final decision and signup, you need to match all the details of their plans and pick the most optimal solution for you website.

Let’s make a test draft of the desired VPS:

Pick the desired disk space quota, we consider it 50 Gb coming with 512 MB RAM -> this means you can have cPanel installed without any problems -> this in turn means, you need CentOS, or any other Linux distro. The choice of cPanel also means, that you may have LAMP configuration set freely. Finally, virtualization type -> you have enough RAM for your server functionality, so no need in burst-RAM seems to emerge. On the other hand, 50 Gb of disk space is enough to share 1 GB for swapping.

Or another option:

Imagine you are a starter. You need the simplest VPS and you get it: 20 GB of disk and 256 MB of RAM. Not much to host a site, which would beet up Youtube or Facebook, but it’s your own virtual server! Let’s go: as there is not much RAM you may forget about cPanel -> this enables you to choose FreeBSD as an OS and Nginx or LiteHTTPD as a webserver. We seem to be getting a pretty light server. To finalize it, we choose OpenVZ to save the disk space and be able to temporarily boost our RAM up.

Summary

We need to admit, that the drafts provided were made up without sites differentiation in mind. We took it for average, to show how this analytic procedure should flow and what the choice of this or that configuration should be based on. There are, however, many sites and many site-building technologies. Each of them has its own peculiarities. This is the very point, were are going to tell about next time. So, await Part 2 released soon.

There is a correspondent discussion raised on our Facebook page. Feel free to take part.

Scripts Resource Intensity

Nowadays having a personal website is as common as having a cell phone. Some people use cell phones for just giving and receiving calls and messages and some cannot simply imagine their mobile telephony device without a camera, an MP3-player and so on. It really is likewise about the websites: some website owners use their hosting accounts to bring up pages on the web and use email at their own domain. The others want their websites to be an ultimate public project, which would support many options starting from integration with social networks and ending with, but not limited to provision of downloadable content.

The way the sites are built is a question of demand, of course. But this question raises another one in turn – a question of approach. Many website owners start with shared hosting but then face with the problem of resource overuse, as their projects keep developing. And that’s where the question of approach becomes essential – those who take such issues seriously usually decide to upgrade in order to avoid temporary suspension due to excessive resource usage.

Of course, the website owner may not always realize the influence of his/her particular account on the entire server. On the other hand, server administrators are always glad to assist with the resolution of the problem. Those suspensions are mostly a preventive measure, which doesn’t let the entire server go down. For example, our team is always open for a dialogue and we co-operate with our Customers to find out the way to get the issue resolved. However, if it is definitely not about some particular script or module which is enough to be disabled to let the account keep working on the shared server – an upgrade is the next step.

VPS as a Hosting Ground for Resource Intensive Websites

Several years earlier the word “upgrade” would definitely mean a setup of a dedicated server, which would be tens times more expensive, than a shared hosting plan you used to have. Modern technology, however, has introduced a more liberal solution – Virtual Private Server (VPS). Those virtual servers are containers, created by means of virtualization software on physical servers. Current platforms allow a VPS web hosting user to obtain almost the same level of performance as the server-carrier provides, which means that a user can get a dedicated server, though a virtualized one, for a significantly cheaper price.

A virtual server has the following key advantages, which are to be considered during the upgrade:

1. Isolation – none of several virtual servers on the carrier influences each other. No limitations are set.
2. Full root environment – the user is provided with the maximal administration privileges.
3. No hardware dependencies – server does not require file system checks and RAID array rebuilds after reboot.

As you can see, a VPS resolves the main concern of a shared hosting account user – mutual user dependency. The thing is that shared servers have such strict limitations primarily due to the problem of even resource distribution, i.e. those limits create fair equal conditions, which let any user run his/her applications without abusing the other accounts. This equality is also guaranteed on a server software level – all major services, like Apache, MySQL and PHP are configured in a standard way and can be slightly tuned up only on a user level by means of local configuration files (e.g. .htaccess, php.ini, etc.).

VPS web hosting, however, provides each user with isolated environment. This means, that there is no one to share resources with, i.e. there are no limits and that any server software may be tuned up according to the peculiarities of the hosted script/application.

Optimizing your WordPress Blog Performance

There are many scripts which require certain tune up. The more tasks a script is to carry our, the finer the tune up should be. As an example we take WordPress blogging tool, which is known for its resource usage peculiarities and a wide range of available plug-ins.

Surely, WordPress is one of the greatest scripts on the Web. This blog tool lets you create a nice and usable website by means of a user-friendly easy-to-comprehend interface. Its basic configuration is fine to be hosted on a shared hosting server and we offer a special plan Blog Hosting with WordPress preinstalled to those, who would like to start their own blog. Still, this platform is a rather resource intensive one, so depending on your goal and means of project realization, you may need to have your account upgraded.

Of course, it is essential to find out, what exactly makes WP resource intensive. Primarily it is the way, it works with the databases. Below you can find an example of a MySQL request created by one user, who is viewing one WordPress page:

3 Query       SELECT option_name, option_value FROM wp_options WHERE autoload = ‘yes’
3 Query       SELECT option_value FROM wp_options WHERE option_name = ‘rewrite_rules’ LIMIT 1
3 Query       SELECT SQL_CALC_FOUND_ROWS  wp_posts.* FROM wp_posts  WHERE 1=1  AND wp_posts.post_type = ‘post’ AND (wp_posts.post_status = ‘publish’)  ORDER BY wp_posts.post_date DESC LIMIT 0, 10
3 Query       SELECT FOUND_ROWS()
3 Query       SELECT t.*, tt.*, tr.object_id FROM wp_terms AS t INNER JOIN wp_term_taxonomy AS tt ON tt.term_id = t.term_id INNER JOIN wp_term_relationships AS tr ON tr.term_taxonomy_id = tt.term_taxonomy_id WHERE tt.taxonomy IN (‘category’, ‘post_tag’) AND tr.object_id IN (10) ORDER BY t.name ASC
3 Query       SELECT post_id, meta_key, meta_value FROM wp_postmeta WHERE post_id IN (10)
3 Query       SELECT * FROM wp_posts  WHERE (post_type = ‘page’ AND post_status = ‘publish’)     ORDER BY menu_order ASC
3 Query       SELECT option_value FROM wp_options WHERE option_name = ‘page_for_posts’ LIMIT 1
3 Query       SELECT * FROM wp_users WHERE ID = 1 LIMIT 1
3 Query       SELECT meta_key, meta_value FROM wp_usermeta WHERE user_id = 1
3 Query       SELECT * FROM wp_comments WHERE comment_post_ID = 10 AND comment_approved = ’1′ ORDER BY comment_date_gmt DESC
3 Query       SELECT * FROM wp_comments WHERE comment_post_ID = 10 AND comment_approved = ’1′ ORDER BY comment_date_gmt DESC
3 Query       SELECT * FROM wp_posts  WHERE (post_type = ‘page’ AND post_status = ‘publish’)     ORDER BY menu_order, post_title ASC
3 Query       SELECT t.*, tt.* FROM wp_terms AS t INNER JOIN wp_term_taxonomy AS tt ON t.term_id = tt.term_id WHERE tt.taxonomy IN (‘category’)  ORDER BY t.name ASC
3 Query       SELECT wp_comments.* FROM wp_comments JOIN wp_posts ON wp_posts.ID = wp_comments.comment_post_ID WHERE comment_approved = ’1′ AND post_status = ‘publish’ ORDER BY comment_date_gmt DESC LIMIT 15
3 Query       SELECT COUNT(comment_ID) FROM wp_comments WHERE comment_post_ID = 12 AND comment_parent = 0 AND comment_approved = ’1′ AND comment_date_gmt < ’2010-02-22 16:54:11′
3 Query       SELECT COUNT(comment_ID) FROM wp_comments WHERE comment_post_ID = 12 AND comment_parent = 0 AND comment_approved = ’1′ AND comment_date_gmt < ’2010-02-22 14:25:24′
3 Query       SELECT COUNT(comment_ID) FROM wp_comments WHERE comment_post_ID = 12 AND comment_parent = 0 AND comment_approved = ’1′ AND comment_date_gmt < ’2010-02-08 18:51:45′
3 Query       SELECT COUNT(comment_ID) FROM wp_comments WHERE comment_post_ID = 12 AND comment_parent = 0 AND comment_approved = ’1′ AND comment_date_gmt < ’2010-01-29 02:58:05′
3 Query       SELECT COUNT(comment_ID) FROM wp_comments WHERE comment_post_ID = 12 AND comment_parent = 0 AND comment_approved = ’1′ AND comment_date_gmt < ’2010-01-29 00:23:01′
3 Query       SELECT YEAR(min(post_date_gmt)) AS firstyear, YEAR(max(post_date_gmt)) AS lastyear FROM wp_posts WHERE post_date_gmt > 1970
3 Quit

MySQL queries of the *SELECT type are one of the most abusive as they go over all the databases to find the needed value. This results into aggressive disk subsystem and CPU usage. By the way, the log above was for a simple WordPress page, which had no add-ons or plug-ins, so you can imagine, what it is going to be, if WordPress is run full-throttle.

It is absolutely logical to search a way for optimization of such queries, as far as the fewer queries are produced, the more free CPU time is left for other server services. That’s what caching is used for. All you need is to edit your wp-config.php file by adding the following two lines there:

// Enable the WordPress Object Cache:
define(ENABLE_CACHE, true);

But this is minor SQL optimization. Another reason for WordPress issues is webserver overload, caused by simultaneous http requests. WP does not offer any other built-in caching tools and the one –WP Super Cache, which is available as a plug-in – is rather resource intensive, so it is allowed for use on VPS and dedicated servers only (AUP, p. 10.1). WP Super Cache is a static caching plug-in, which generates html files that are served directly by Apache webserver without processing comparatively heavy PHP scripts. This plug-in is one of the means to increase your WordPress blog performance significantly.

Still, this is not all what you can do for webserver optimization. Now you should edit your Apache configuration file (full path: /etc/httpd/conf/httpd.conf) as follows:

Note: Before you proceed with file editing, make sure you backed-up your configuration file.

# Timeout and Keepalive
Timeout 30
KeepAlive On
MaxKeepAliveRequests 100
KeepAliveTimeout 6

#Maximum Client Connections
&lt;IfModule prefork.c&gt;
StartServers       8
MinSpareServers    5
MaxSpareServers   20
ServerLimit      512
MaxClients       512
MaxRequestsPerChild  4000
&lt;/IfModule&gt;

Note: MaxRequestsPerChild parameter is a tricky one, so 4000 is not the fixed value, you may try a range from 1000 to 4000 to see, which configuration is better and leave it.
Note: #Maximum Client Connections may be not available in the configuration file, if “prefork” Apache module is not configured (if not, there’s a “worker mpm” module installed instead).

Once the file is edited, restart Apache with the following command: /etc/init.d/httpd restart.
Additionally you may consult more online guides on disabling those Apache modules, you are not using.
Such modules take CPU time and RAM to get loaded and then simply do nothing, while you can comment them out in the configuration file.

Another service to edit is PHP. Find a global php.ini file (should be located there: /usr/local/lib/php.ini) and copy it to the root folder of your WordPress. Open it for editing to set the following parameters:

;*Turn off for performance
register_globals = Off
register_long_arrays = Off
register_argc_argv = Off
magic_quotes_gpc = Off
magic_quotes_runtime = Off
magic_quotes_sybase = Off
;*Allow PHP to accept large data
post_max_size = 8M
file_uploads = On
upload_max_filesize = 8M

Conclusion

We really hope you find these tips useful. Those are not the only ones, of course, so you can find many other ways of WordPress optimization, which may come in handy. It is still advisable to consult your technical support team before making any changes to the essential services on your server and of course, do not forget to backup your initial configuration files.

Many of web hosting newbies bring up a question about differences between a reseller hosting and a VPS and wondering which one is best for their project needs. Unfortunately, it is not that simple to answer this question. There is a number of touches that require a closer investigation on the subject to give a decent answer. First of all, a lot depends on the initial aim, i.e. whether the account will be used to resell hosting, utilized directly to host own content, used as a test ground for products in development or all at once. Moreover, Skills possessed by an owner of an account matter a lot as well as the price differences. Let’s take a closer look at both hosting types to draw reasonable conclusions…

Shared Reseller Hosting Plans

Reseller hosting is a variation of a shared hosting, which in turn is a kind of a budget solution for those who are just starting off or have moderate needs. The idea behind shared hosting is quite simple – a lot of accounts on one single physical server. It is basically a dedicated server with installed OS and set of software. All of the accounts share resources and are restricted to use them for limited amounts of time. If an account violates the restrictions, it gets frozen or suspended for abuse. Policy violators cause overall slowdown for other users on the server because they use everybody else’s resources. While a dedicated server costs a lot of money, a shared account is very cheap (around $5-10 per month versus $200-700 for a dedicated server).

Installed and configured sets of software are available to everyone on a shared server, and only a small amount of adjustments can be done to this software due to the fact that it is used by all accounts. In most cases specific software sets cannot be installed at all. Administration privileges are limited to a simple user. Therefore, all important configurations are done by system administrators.

Reseller shared hosting plans have more functionality though and allow creating other hosting accounts. This way an owner of a reseller plan becomes a user with advanced privileges as compared to regular resold account users on the server. He can create, modify and delete hosting accounts according to the limits of the plans. In everything else he is pretty mush no different form a regular user.

Virtual Private Servers

Virtual Private Server is a special kind of hosting account located on a real carrier dedicated server. These virtual containers are created with the help of virtualization platforms. Latest advances in virtualization technologies provide VPSs with performance levels almost identical to the ones of its carriers. That means that now it is possible to have a lighter “virtual” dedicated server at prices, which are far cheaper than a physical one would actually be. As a matter of fact, a single real machine can now be in a way separated into several parts while every part will still posses features of the original system. The main distinction of a VPS is that it is fully isolated from other similar units on the same carrier dedicated server. Root access is no longer a restriction on VPS. This opens up full customization and administration capabilities. Many software sets and bundles can be installed and configured to your preference on a VPS.

As you can see, resource limitations that exist on shared accounts are no longer of any importance for VPS owner. He himself creates limitations and policies and decides the way all resources are used. However, it is important to remember that amount of available resources is limited. As the entire VPS runs on a set of several software products, including an OS, it is crucial not to deplete the resources. It is also important to keep in mind that a VPS is normally not as powerful as a server which hosts shared plans. That means that part of the VPS resources is spent on a general system functioning upkeep. Therefore, resource depletion will cause downtime of an entire VPS. Such downtime will include a need to reboot the container the hard way (i.e. by power reset). However, unlike a real server, when a VPS is incorrectly rebooted during hanging, there is no need for file system check or RAID rebuild, because these things are controlled on the side of the carrier server.

Bottom line

Hopefully, the information given above will help beginners better understand the differences between a VPS and Reseller hosting. VPSs are more powerful, provide more freedom, require more administration and cost a lot more than reseller accounts. On the other hand, reseller plans are relatively cheap, are fully managed by hosting company and are at the same time limited in features. Resource problems caused by a single account immediately may lead to service problems for an entire VPS. On the contrary, resold account taking up too much resources will lead to suspension of itself only, keeping all other accounts created by reseller online. Of course, there are more peculiarities in differences between the two, but it is quite obvious that a VPS is a choice for an experienced user with some skills of administration. Reseller hosting, on the other hand, is the best option for beginners. At the end of the day you can start with a reseller and then upgrade to a VPS if you feel need to.

Take a few seconds and check out our extremely cheap prices for shared, VPS and dedicated server plans at Sitevalley.com

Virtualization is a widely used technology nowadays. A whole set of hosting plans is based on it – the so-called Virtual Private Servers (VPS). They allow steady transition from regular shared to the most powerful dedicated solutions. While big projects may require the power of an independent dedicated server, some personal and small-to-medium businesses may not need such resources at high costs at first. At the same time the needs of  such customers may not be satisfied with what regular shared hosting has to offer due its nature . Unlike shared hosting, V PS allows full isolation from other users on the host server. It provides full control over the account (i.e. root access), remote reboots and system restore.

Nowadays various approaches and implementations of virtualization exist. In this article we will compare two most widely used virtualization engines: OpenVZ and Xen. The main goal of the article is to provide basic concept, and outline the differences and similarities of the two engines.

Virtualization

As defined by Wikipedia virtualization is a term that refers to the abstraction of computer resources. In case of VPS  hosting plans, platform virtualization is used. Its idea is to separate an operating system (OS) from hardware it is being run on. With no virtualization applied, normally only one operating system can be run on one set of hardware at the same time. As depicted in the Figure 1, every server composed of a definite hardware set can simultaneously run only one OS, however, if the virtualization technology is applied, one achieves the ability to have numerous OSs run on single set of hardware at the same time:

Figure 1. Application of virtualization. Source: http://mysite.stonybrook.edu/

As we can see, the virtualization is used to create an independence from the hardware for an OS. Virtualization software not only allows to run several OSs on the hardware, but also separates the resources a single OS is consuming. This way various quotas for CPU, RAM, HDD I/O and such can be defined for a single OS. Quota based isolation increases the utilization of a single dedicated server by dividing resources of the latter into smaller chunks. This is quite efficient as it decreases the cost of a single VPS and, at the same time, provides new unique features to the user.

Paravirtualization

In order to understand how virtualization works let’s consider its structure (see  Figure 2 ). As we can see form the figure, main idea of virtualization is creating a special interaction layer (Virtualization layer) between the hardware and OS which acts as a resource isolator and manager at the same time:

Figure 2 Basic structure of virtualization. Source: http://desktop-virtualization.com

Figure 2 shows a special case when the virtualization layer is placed directly on top of the hardware (architecture) and then the OSs are installed on top of the virtualization layer. Consequently, the applications such as Apache Web Server and MySQL server are run on top of the OS and do not interact with the applications run on the other OSs. This way the depletion of resources given to one OS does not influence the performance of the other OSs on the hardware carrier server. Such isolation eliminates the possibility of overloads caused by other users on the carrier. This kind of virtualization can be referred to as to a Paravitualization.

As defined by Wikipedia paravirtualization is a virtualization technique that presents a software interface to virtual machines that is similar but not identical to that of the underlying hardware. This technique is used in the XEN virtual engine. Paravirtualization has a number of limitations, one of which being a special need for slight modification of the OS kernel in order to teach it to use the instructions given by virtualization layer. Such need, however, can be avoided by utilization of special processors supporting the hardware assisted virtualization technology. A processor with such capability can help the software virtualization layer to perform the abstraction. This way no modification is required to be performed to the OS, and therefore any proprietary software like Microsoft Windows can be run on the virtualization layer. Not only it allows for running of proprietary technologies, but it also lets using the original form of the OS which can be important for a number of applications run on it.

Operating system-level virtualization

Paravirtualization is not the only type of the virtualization used in hosting industry. Another widely used type is Operating system-level virtualization (OSLV). This kind is defined In Wikipedia as a method where the operating system allows for multiple user-space instances (virtual hosting, chroot jail + resource management). This means ,that only one OS with only one kernel is running on the server. OS is modified in such a way that it allows for creation of so-called containers which appear as a separate OS entity to the user and software within that container. This can be depicted as shown in the Figure 3:

Figure 3 Basic structure of Operating system-level virtualization. Source: http://www.linux-watch.com

This type of virtualization is implemented in the OpenVZ engine. Resource sharing in such structure differs from the paravirtualization. In the latter technology the resources are firmly distributed on the virtualization level, and no sharing takes place. In the OSLV all containers (VPSs) are running in the same environment. The resources of each one are assigned and limited. However, there is a certain amount of the resources that is kept for sharing within the host OS and is not assigned to any specific VPS. If such resources are not occupied by host system, any VPS can use them if necessary. An example can be given in terms of a burstable RAM. There is a guaranteed RAM quota VPS always has, and there is also a top limit of burstable RAM this VPS can also use in case the system has any additional free RAM besides the amount already guaranteed and provided.

In OSLV all containers run inside a single host system. Each container emulates an OS within itself, but it can only emulate the OS kernel which is similar to the one the container itself is running in. This is a great limitation. OpenVZ is run on Linux OSs. Therefore, the only OS that can be installed in the containers within the carrier is of Linux. This way usage of FreeBSD is simply not possible within the OpenVZ based VPS. At the same time, there is no problem using FreeBSD in a paravirtualized environment like Xen.

Xen vs OpenVZ

Xen

Figure 4 Xen paravirtualization architecture. Source: http://uberhip.com

Xen is a virtualization engine (to be exact it is a virtual-machine monitor) for x86, x86-64, Itanium and PowerPC platforms. On number of processor a paravirtualization technique is applied by Xen. This means that the operation systems run on Xen are modified in order to achieve high performance on a wide range of hardware architectures, which are initially not intended for virtualization technologies. The architecture of Xen is presented in Figure 4.

Xen uses one privileged OS to control the hardware resources. This privileged OS must be a Unix based one (e.g. Linux, FreeBSD etc.). In the latest versions of Xen the following OSs can be run as guest ones:Linux, Minix, Plan 9 from Bell Labs, NetBSD, OpenBSD, FreeBSD, OpenSolaris, NetWare, GNU/Hurd/Mach, OZONE.

OpenVZ

Figure 5 OpenVZ operating system-level virtualization architecture. Source: http://www.linux-watch.com

OpenVZ is an open-source virtualization engine on the x86, x86_64, and IA64 processors. OpenVZ, itself, is built on top of Linux. Unlike Xen’s paravirtualization technique, with OSLV virtualization the operating environment is virtualized instead of the hardware. Thus, while there is only one operating system kernel, multiple programs run in isolation from each other within the single OS instance. The basic architecture of OpenVZ is shown in the Figure 5. OpenVZ project manager Kir Kolyshkin said in a statement about its architecture:

“Unlike hypervisor-based virtualization technology [such as Xen and VMware], OpenVZ is extremely easily portable across different architectures, since 95 percent of the code is platform-independent. With the port to Power, we’ve opened the door for another segment of the user community to benefit from our open source virtualization software”.

Differences and Similarities.

Both system present the user with the following benefits:

• consolidation
• increased utilization
• rapid provisioning
• dynamic fault tolerance against software failures (through rapid bootstrapping or rebooting)
• hardware fault tolerance (through migration of a virtual machine to different hardware)

Resources

Additionally both Xen and OpenVZ provide the the ability to securely separate virtual operating systems. However, this feature is implemented through different techniques in these two virtualization solutions. Xen provides full fixed isolation, where the initially assigned quotas are kept throughout the entire functioning period, and additional request for memory are processed using the swap space on the HDDs. OpenVZ ,on the other hand, provides semi-dynamical assignment of resources. Such terms as burstable RAM and resources exist on OpenVZ. Therefore, unlike the case with Xen, VPSs based on OpenVZ may also take advantage of the free resources of the server. This can result in better utilization of the resources of the carrier hardware.

Performance

The virtualization overhead observed in both OpenVZ and Xen is limited. Various opinions exist on the difference in performance between the two. However, in both cases the performance levels of virtualized environment, as compared to the real hardware, are of acceptance-quality level. Specific figures depend on a great number of factors and cannot be summed up for the general conclusion.

Compatibility

Unlike OpenVZ, XEN has the ability to support legacy software as well as new OS instances on the same computer. That means that proprietary systems can be installed on Xen based carrier without any additional modification if hardware assisted virtualization is used. OpenVZ provides compatibility only in frame of the alike kernel, such as various distributions of Linux OSs.

Migration

Both provide great and relatively equal check pointing and live migration options.

Scalability

Both engines are based on the Unix OSs, therefore they have great scalability. For example in case of OpenVZ which employs a single kernel model, it is as scalable as the Linux kernel. Such kernel supports up to 64 CPUs and up to 64 GB of RAM. (on 32-bit with PAE) A single container can scale up to the whole physical system, i.e. use all the CPUs and all the RAM.

Management

Peculiarity of OpenVZ is the mass management support. An administrator (i.e. root) of an OpenVZ physical server (carrier) can see all the running processes and files of all the containers on the system. That makes mass management scenarios possible. Let’s look into the case in which  Xen is used for server consolidation: in order to apply a security update to 10 virtual servers, an administrator is required to log in into each one and run an update procedure. Since VPSs are normally indented for different users with their own projects, this is not an issue for Xen based virtualization. However, the fact that with OpenVZ a simple shell script can update all containers at once greatly eases the management of the entire system.

Conclusions

Virtualization basics as well as the main principles of two fundamentally different virtualization solutions have been described in this post. It is obvious that both projects are outstanding virtualization systems and provide host industry with sufficient number of features to support an entire type of VPS plans. Each of the engines is aimed at solving specific set of tasks, which they successfully do. Xen is a technology mainly aimed at providing the maximum approach to the full virtualization and full separation of virtual machines on the hardware carrier. It is also aimed at supporting the maximum range of existing operating systems. OpenVZ, on the other hand, is a system specifically aimed at Linux based virtual environments. It provides good dynamic resource sharing and isolation tools, which leads to higher server utilization figures. Both engines show great performance.