Posted: October 3rd, 2012 | By: Chris_C | Filed under: OpenVZ, Wordpress, Xen | Tags: content management system, DNS server, Intel Xeon, MySQL, OpenVPN, OpenVZ, VPS hosting, web server, Wordpress VPS, Wordpress Wednesdays, Xen | No Comments »
This is a very common question and there are tons of information on the Internet about what the minimum requirements are and what to avoid so let me clear up some of the confusion.
This is part of an ongoing series of “WordPress Wednesdays” and in the month of October we will discuss on this website what kind of virtual private server do we need to run WordPress, a popular content management system that operates a significant amount of websites including blogs, websites just like this and even many news websites such as from CBS Local all run WordPress because of it’s flexibility.
OpenVZ or Xen?
A very good question indeed!
OpenVZ would be the bare minimum I would use for WordPress hosting while if you have a medium to large traffic website or require a lot of plugins, caching, etc. I would go with Xen VPS hosting for WordPress hosting which is generally only a few more dollars more in comparison to OpenVZ but the performance is worth those few extra dollars.
A VPS server’s CPU and hardware are often overlooked by individuals who are primarily focused on price!
WordPress is not CPU intensive, however MySQL which powers the WordPress content management system is, so if you go out and get a $3 VPS which has 128mb RAM, 10gb of disk space and only one CPU – do not be surprised if that medium or high traffic WordPress based website starts to crawl!
I’m sure you see guys on forums talking about they have WordPress running on a 32mb – 64mb VPS but please do not even consider shorting yourself on memory. If you want 32mb of memory dedicated to running your WordPress blog, why did you even leave shared web hosting?
A budget motivated website owner will get a custom VPS with more than enough RAM, disk space and bandwidth but only get one or two CPUs for a website that receives thousands of visits during peak hours!
Don’t short yourself on CPU!
To put things into perspective, how many single core processor desktops and laptops do you own?
If you own one, they’re slow as molasses when you’re trying to watch high definition video right? Same concept with a virtual private server – one CPU works for DNS servers, OpenVPN servers and web servers offering static files like images and HTML files but if MySQL is involved in your project and a dependency, 2 CPU cores are a minimum I would consider with 4 or more CPUs as what would be acceptable to me.
It does not matter if you have Intel Xeon or AMD based CPUs on your server. 8 CPUs at 1Ghz with an AMD based system is just as good as 2 CPUs running at 3Ghz on an Intel Xeon system.
The problem you had when you were on shared hosting running your WordPress site was your CPU and memory was limited. Most memory available to shared web hosting customers is anywhere from 8 – 32mb to run their PHP web applications. If you have multiple plugins, including a sitemap generator, this is where you would get all the weird errors, blank pages and what generally drove you away from shared hosting to virtual private server hosting.
With our first lesson on “WordPress Wednesdays”, we have learned that OpenVZ and Xen does not really matter when it comes to running a WordPress site.
With OpenVZ, all the resources are shared with “your neighbors” on the same VPS node like shared web hosting and with Xen, your resources are guaranteed. Xen is only a few more dollars than OpenVZ but I think resource guarantees are worth the few extra dollars.
We also learned that CPU is something often overlooked by VPS hosting customers but should be emphasized more than anything. Would you drive a sports car if it only had a two cylinder engine inside of it that would be fast as a lawnmower or do you want the V8 engine, with 8 cylinders powering the sports car, which could be similar to an 8 CPU core system?
Thank you and tune in for next Wednesday’s article where we discuss if we should consider Apache or nginx with our WordPress website.
Posted: September 28th, 2012 | By: Chris_C | Filed under: OpenVZ, Reviews, Xen | Tags: KVM, OpenVZ, what kind of VPS do I need, Xen, Xen HVM, Xen PV | No Comments »
This is a common question and a lot of people don’t understand that “one size fits all” does not apply when it comes to VPS hosting. It should be “one size fits most.”
OpenVZ, in my opinion, is a step up from web shared hosting but still has the shared hosting feeling because of shared resources. In my experience I notice the usual transition is that a shared web hosting customer will be kicked out or suspended from the hosting company for using too much I/O, such as attempting to run a forum or a heavy traffic WordPress blog, or the customer is tired of WordPress timing out on upgrades.
OpenVZ is cheap and is attractive to 99% of the interested customers however:
- You have to share resources with your “neighbor” on the server.
- If your “neighbor” has tons of traffic hit his WordPress blog, which puts load on his MySQL server, you and everyone else on the server is going to feel it because of the CPU demand.
Xen, in my opinion, is the preferred VPS hosting that I recommend to individuals where the website has to be up, fast and reliable but the customer has the money in their budget to pay for the price difference. The difference is usually a few dollars and honestly, how much is your downtime or reliability worth?
Xen comes in two options: Xen PV and Xen HVM.
Xen PV, or paravirtualization, is like OpenVZ in the fact that Xen uses templates like OpenVZ and reinstalls can be done from the control panel.
HVM allows you to mount and install an ISO, like a dedicated server, and gives you more options for operating systems like *BSD operating systems that are not supported by OpenVZ. Xen HVM supports Windows and is how most Windows VPS servers are powered.
KVM is a popular alternative to Xen and just as recommended as Xen. I have no personal preference between Xen and KVM except that if Xen HVM is unavailable and you need to install from ISO, that KVM is just as good as Xen HVM.
The pricing is generally the same between KVM and Xen HVM.
With all the available options, if you are looking for a “step up” from shared web hosting to a virtual private server and lack the system administrator experience, OpenVZ is a good choice. Also, if you have a limited budget OpenVZ is just a good choice.
If you need something as easy to use as OpenVZ but want reliability, Xen PV is a good choice for a few dollars extra to get better, guaranteed resources and a more reliable VPS than OpenVZ.
If you want customization of installing your own ISO or Windows VPS, Xen HVM or KVM is good. Both are as equal and reliable so I have no personal or professional preference.
Posted: August 13th, 2012 | By: Rob_K | Filed under: Featured, OpenVZ, Xen | Tags: Linux, OpenVZ, VPS, Xen | No Comments »
The question is often asked whether OpenVZ or Xen, two of the most common hypervisors in VPS web hosting, provides a faster hosting environment.
The most common answer to this question is that “OpenVZ is faster,” even though this is not strictly true. OpenVZ’s virtualization is managed at the operating system (OS) level, compared to Xen’s paravirtualized or fully hardware-virtualized environments. Hence, OpenVZ requires slightly less resource overhead, and can be seen as a more resource-efficient hypervisor — but not necessarily a “faster” one.
Compared to performance that would be measured for an application running directly on the physical server, all virtualization techniques will result in at least a small loss in performance due to the hypervisor’s resource overhead. Since most VPS hosts power their host servers with high-quality hardware, this loss in performance is hardly perceptible.
However, the question remains as to whether the Xen or OpenVZ hypervisor achieves better performance. The simple answer is that there are a great number of factors which could determine an answer one way or another, but there are certain key factors which set the two system apart.
It is important to note the methods Xen and OpenVZ use to assign resources to VEs. On an OpenVZ host server, where all of the server’s physical hardware resources “belong” to the host server and VEs differ only in the operating systems they are running, each VE will essentially have access to the entire server’s resources. Although there are “soft limits” placed for each VE to prevent over-usage of RAM, disk, and other resources, these limits can be (and are frequently) bypassed and abused. For this reason, the performance of an OpenVZ VPS can vary wildly depending on how many other VEs are on the same host, and what they are doing.
In contrast to OpenVZ’s OS-level virtualization, Xen virtualizes hardware and network resources at a deeper level, and provides near-total isolation for each individual VE. It is well-known that Xen VPS instances can run their own isolated kernels, but this more advanced hypervisor confers other benefits as well. A Xen VPS is guaranteed its resource allocations in such a way that it is impossible for neighboring VEs to “steal” them, which means that Xen environments are far more reliably stable than OpenVZ environments.
Resource Over-commitment (Overselling)
A side-effect of these virtualization techniques is that Xen host servers cannot be oversold, while OpenVZ host servers are frequently oversold (in fact, this is why OpenVZ hosting is typically less expensive than Xen). Overselling is the practice of over-committing the host server’s resources in such a way that the server could not actually sustain itself if each VE requested 100% of the resources it is “guaranteed.” Since Xen dedicates resources to each VE which are then no longer available to the host system or any neighboring VEs, it is not possible to over-commit a Xen host’s resources.
Security & Stability
For the same reasons mentioned above — namely, that OpenVZ containers take their resources freely from a “pool,” while Xen containers have their own dedicated resources — OpenVZ is also prone to flaws impacting system security and stability.
Since OpenVZ virtualizes at the OS level, all hosted VEs essentially share the same host-level kernel. Because of this, a kernel exception caused by one container can crash the entire host server, affecting all other co-hosted VEs. Similarly, OpenVZ hosts use a single iptables and single network interface to mediate incoming/outgoing connections, as well. The results are easy to imagine: if one VE pushes too hard (even accidentally), the others will suffer.
Each Xen environment is “locked in” to its container, which makes it comparatively impossible to abuse the host system in a way that would affect neighboring VEs. For this reason, Xen VPS are considered far more reliable and secure, and can be likened more to dedicated servers in terms of their structure and features.
With all of this in mind, it becomes clear why OpenVZ is often said to be faster than Xen, and sometimes even appears that way in benchmarks — the benchmarks compare [b]empty OpenVZ systems to empty Xen systems, as would be typical in an objective, testing environment.
In a real web hosting environment, however, host servers will be bustling with activity by the time you get there, which makes a Xen VPS is a much better guarantee to have — it means having the peace of mind knowing that the resources you need will be there when you need them.
Although it is true that OpenVZ is marginally “faster” due to the hypervisor’s decreased resource overhead, this difference is not tangible in actual usage, and will manifest only as a slightly smaller amount of available RAM on freshly installed Xen VEs.
So, here is the final answer:
In Theory, OpenVZ provides a faster virtualized environment due to the fact that the VE is directly supported by the host system, and therefore uses less of its own resources to maintain its OS.
In Practice, Xen reliably outperforms OpenVZ, especially among budget-oriented web hosts where practices like resource over-commitment are common.
This article is also available in the VPS6.NET Knowledgebase: https://vps6.net/my/knowledgebase/69/OpenVZ-or-Xen-VPS—Which-is-faster-and-which-is-better.html
Posted: June 22nd, 2012 | By: Rob_K | Filed under: Security & Optimization, Tutorials, Windows, Xen | Tags: GPLPV, PV-on-HVM, PVonHVM, Windows, Xen | No Comments »
The GPLPV package is a driver for Microsoft Windows, which allows Windows systems virtualised with Xen (such as VPS6.NET’s) access to the network and block drivers of the Xen dom0. These drivers provide a significant performance and reliability gain over the standard devices emulated by Xen, and are recommended for anyone using our Windows VPS service.
Installation of the package is simple, and has no known compatibility issues with any our systems.
- From the desktop of your Windows VPS, download the file matching your system:
- Run the .msi file and follow the on-screen directions to complete installation.
- Check the Device Manager for “Xen Net Device Driver” and “Xen Block Device Driver”, which indicate a successful installation.
- Reboot the VPS, either from within Windows or from SolusVM.
Your system should now experience enhanced network and disk speeds!
This article is also available in the VPS6.NET Knowledgebase: https://vps6.net/my/knowledgebase/68/How-to-Install-GPLPV-PV-on-HVM-Drivers-on-Windows-Server-2008-Systems.html
Posted: January 2nd, 2012 | By: Rob_K | Filed under: Featured, OpenVZ, Xen | Tags: OpenVZ, Xen | No Comments »
We’ve written this article to provide a little insight and guidance as to the difference between Xen and OpenVZ, two very popular but somewhat different virtualization technologies. Ultimately, as with choosing between a Linux or Windows server, you will need to think about the applications you will be running to decide whether OpenVZ or Xen will be a better fit for you. Below is a brief summary of some of the key differences between these two platforms.
The slightly more reliable virtualization software is Xen, a para-virtualization platform that creates virtual servers with almost exactly the same characteristics as dedicated servers. A Xen VPS will run its own isolated kernel, load its own kernel modules, use fully dedicated virtualized memory, I/O and scheduler, and will be just as stable and extensible as a dedicated server. You’ll never know that you’re only using a virtual server — for a small premium.
OpenVZ, on the other hand, is an operating-system-level virtualization platform that works in much the same way, but provides only a thin layer of virtualization on top of the underlying OS. All virtual servers on an OpenVZ node will share the same core Linux kernel–this is why OpenVZ only supports Linux OS templates–, and, consequently, will also suffer alike from issues like kernel crashes. Despite these small drawbacks, OpenVZ is more cost-effective, easier to understand, and usually performs much better for small virtual servers, due to having the extra resources available that a Xen VPS would be using to run its completely isolated environment.
Main Features of OpenVZ Virtualization:
+ Full root access.
+ OS-level virtualization.
+ ‘Burst’ RAM and other extra resources available when nodes are underused.
+ Upgrades can be applied on-the-fly, without reboots.
+ More resources available due to lightweight virtualization.
+ Simple network and disk setup.
+ Access to most iptables modules.
Main Features of Xen Virtualization:
+ Full root access.
+ Supports Linux and Windows.
+ Better Java performance.
+ Resources (RAM, etc) are fully dedicated and private.
+ Para-virtualized Linux kernel (i.e., full isolation).
+ Direct access to loadable kernel modules.
+ Swap space.
+ Highly configurable.
If you are in doubt about which platform would be better for you, OpenVZ will most likely offer an easier-to-setup and more cost-effective solution, unless you know in advance that you will require specific kernel modules that OpenVZ may not support.
This article is also available in the VPS6 Knowledgebase: