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.

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.

Not that long ago we published an article introducing you into cloud hosting. This relatively new, yet powerful and promising technology becomes more widely used in hosting of small and medium online projects day by day. It means that this kind of hosting services gains users trust and requires less technical skills than one might think. Additionally, it makes prospect customers expect further price reduction, which in turn may increase the sales of this product.

If you want to make sure that all your plans regarding your hosting ground get realized, it is vital to do some pre-sales work targeted at finding out as much technical information as possible. Many things about the technology in use are usually available in extended feature list of packages offered by a hosting provider, at their corporate Wiki or FAQ documents. Today we are going to talk about the primary parameter to look after while choosing your cloud host – platform.

Platform for Cloud Shared Hosting

Mentioning small to medium websites was done on purpose, since the owners of such projects form the main layer of shared hosting customers. Being well optimized many websites, even relatively resource intensive ones, can exist on a shared server not requiring any upgrades and without causing any overloads. But what if the account on the server caused minor loads or simply produced load spikes during unexpected visitor rate increase? Virtually it might stay on the same server, if the latter had more resources… or if the account had a fixed limit on each server resource provided. Of course, this would cause slowdowns and even short downtime for the specific account holder, but considering the fact no other server users were affected, no one would ever suspend such an account.

In fact, we really get a shared hosting platform capable of hosting the same or a larger number of users than on a simple shared server and enhanced with dedicated resource distribution – this sounds interesting. Which technology do they use for such solutions? Since it’s a shared hosting platform, you will hardly find any clustered solutions with a lot of physical servers involved. There comes a question, how to create a simpler yet reliable cloud hosting platform, using one physical machine. Composing this review we decided to compare two solutions of such kind.

Standalone Server with CloudLinux OS

If you give a quick look at what the CloudLinux OS is, you will find out that it’s just a CentOS-based build with special patches. The way those patches work, however, truly confirm the “Cloud” prefix in the name of this OS – namely they utilize a kernel level technology enabling per user resource limitation. As a result, no account can use more than the fixed amount of resources assigned. Reminds of the way OpenVZ VPS servers work, doesn’t it? Yes it does, owing to CloudLinux OS all server users are isolated from each other so anytime some of them go down, all the other user accounts stay stable.

Apart from those user-level limitations CloudLinux supports resource-per-application limits adjustment. Thus, if you have several projects hosted under one account, you can distribute the limits, depending on websites priority. Say you’ve got a serious business website that has to be constantly online and you have a corporate blog that may cause load spikes during promos you run or whatsoever. Well, you limit your blog, so next time it’s overloaded it simply goes down on its own letting your business website keep working with no interruptions.

As far as you can see, CloudLinux OS is something that is worth being given a try as a cloud hosting platform. It however has a sole disadvantage that may stop you – your account exists within single environment, so any OS corruption may cause serious downtime or even data loss.

VPS Cloud Hosting

Unlike CloudLinux, VPS Cloud platforms do not provide single environment. Well, the environment you work with is actually single, but in fact it is supported but several VPS servers (VPS nodes). The number of nodes forms the amount of resources available for you. The more nodes you have, the more powerful your platform is… and the more redundant. If your CloudLinux environment goes down, you’ll experience downtime unless the issue is fixed. VPS Cloud never goes down off hand – each node takes care of your environment, restoring all services with minimal downtime, then the nodes that have failed recover and your system gets completely stabilized.

Building cloud on VPS first of all means providing utmost scalability. You can adjust the number of available nodes anytime you need more power, or vice versa – less expenses. Taking to account the initial cost of VPS-based cloud hosting – such scalability can really be considered vital. You may wonder why VPS cloud hosting is so expensive compared to CloudLinux hosting solutions – the reason is hardware. VPS cloud hosting is based on XEN hypervisor technology that implements usage of a more powerful carrier server. Taking into account the fact that each carrier should be able to bear over 20 VPS nodes at minimum – for optimal ROI, the physical machine requires a great shared storage – this involves usage of RAID array solutions with fast (usually SCSI) disks.

What you get for all this – is a completely isolated environment with a way more powerful resource base initially ready for higher loads. Even the lack of root access doesn’t sound like a disadvantage – you can anyway have your environment adjusted, at least with the help of the technical support team of your host.

The Bottomline

Although two platforms look different, you can use both of them for cloud hosting. Can one really call CloudLinux a platform for cloud hosting? Yes, if you need to provide affordable shared hosting with enhanced stability. What is VPS cloud then? It is a solution for more resource intensive projects, but if you are a reseller – you get the same platform as those who choose CloudLinux. Definitely, you are backed by a load of nodes that make your service rock solid but from the point of view of the end user both platforms will look like inexpensive hosting grounds with improved stability and reliability. Thus, if you are looking for a reliable cloud hosting solution – you should check out the platform the service is based on. CloudLinux is going to be cheaper; VPS based cloud hosting may be more expensive, though powerful and redundant, but you can be sure – both services are based on utmost high performance hardware that is monitored and thus secured from failures.

If referring to our personal point of view – Cloud VPS is a more redundant and reliable solution. Taking into account the fact that we at SiteValley.com are looking into starting offering cloud hosting, too – let us announce that having analyzed the given niche we are on our way setting up the first VPS node.

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.

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.