OpenVZ vs. Xen: What's the difference, and which is better?

[VPS6NET]

We've written this article to provide a little insight into the difference between OpenVZ and Xen, 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 them. Below is a brief overview of some of the key differences between these two platforms.

The slightly more reliable virtualization software is Xen, a para-virtualization platform that creates VPS 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 customizable as a dedicated server. For a small premium, you'll never know that you're only using a virtual server.

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 VPS on an OpenVZ node will share the same core Linux kernel--this is why OpenVZ only supports Linux systems--, and, consequently, will also suffer alike from issues like kernel crashes. Despite these small drawbacks, OpenVZ VPS are more cost-effective, easier to understand, and are usually much more effective than Xen as cheap VPS, due to having the extra resources available that a Xen VPS would be using to run its completely isolated environment.

Certainly, these are not the only differences between the two platforms, but they are some of the most significant:

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 unsure which platform would be better for you, an OpenVZ VPS will most likely be an easier and more cost-effective solution, unless you already know that you will require specific kernel modules that OpenVZ does not support.

[Kikito Rodrigues]

I never used xen virtualization, i already had openvz(veportal and solusvm) i think they are better.
But, i never tested the xen, so i cannot give the opinion about that.

[wswd]

I never used xen virtualization, i already had openvz(veportal and solusvm) i think they are better.
But, i never tested the xen, so i cannot give the opinion about that.

Xen is far better than OpenVZ.

[CS Squad]

Xen is far better than OpenVZ as all the resource that a VM have, are allocated dedicatedly to the VM.
So basically, the RAM and disk space you have in your Xen VM,
Well, although not 100% is dedicated resources. You can still over commit a bit by balooning it...

[giangbs]

Xen is far better than OpenVZ.

It depends on provider and hardware. With the same hardware and same provider with the same oversold level, we can't certain which is better But I have heard from a provider which providing OpenVZ, XenPV, XenHVM and KVM, he said that OpenVZ will get best performance in the same hardware

[wswd]

It depends on provider and hardware. With the same hardware and same provider with the same oversold level, we can't certain which is better But I have heard from a provider which providing OpenVZ, XenPV, XenHVM and KVM, he said that OpenVZ will get best performance in the same hardware

With the same oversold server??? You shouldn't be overselling, but unfortunately, that's what most people with OpenVZ do. OpenVZ is in fact slightly better performance wise, but when you weigh in all the factors, Xen isolates the users far better, which is really the purpose of a VPS...an isolated environment, just like a dedicated server.

[CS Squad]

Actually, it depends on what you want to run in the VPS.
If you are going to deploy a JBOSS server, then you should go for XEN instead of OpenVZ.

[giangbs]

With the same oversold server??? You shouldn't be overselling, but unfortunately, that's what most people with OpenVZ do. OpenVZ is in fact slightly better performance wise, but when you weigh in all the factors, Xen isolates the users far better, which is really the purpose of a VPS...an isolated environment, just like a dedicated server.

Oversold is the good way to make more money As long as they are not overloading the server

[wswd]

Oversold is the good way to make more money As long as they are not overloading the server

Uhhhhhh. Okay, maybe that's a good way for your company to make more money. I make more money by being honest to my clients and selling them only the resources that are truly available.

[VPS6NET]

Oversold is the good way to make more money As long as they are not overloading the server

I tend to disagree; overselling 5 or 10% is feasible and probably something most OpenVZ hosts do, but truly "overselling" is never advisable.

[lagoon70]

I would prefer and recommend openvz with solusvm any day over xen

[wswd]

I would prefer and recommend openvz with solusvm any day over xen

And why is that?

[Seraphim]

It depends on provider and hardware. With the same hardware and same provider with the same oversold level, we can't certain which is better But I have heard from a provider which providing OpenVZ, XenPV, XenHVM and KVM, he said that OpenVZ will get best performance in the same hardware

OpenVZ is indeed slightly higher performance, but only because it has a lot less overhead on the node. In practice, the performance gains are more than lost to node saturation and overselling, with many providers pushing their nodes well beyond real resources in the interest of profits. Not only that, but someone on an OpenVZ node using excessive CPU power impacts all other VPSs on the node, something that other technologies avoid.

Xen on the other hand is a little heavier, but because out of the box Xen does not allow for any sharing of RAM at all it is a great deal more difficult to oversell. The end result is that most Xen VPSs will show far better reliability than OpenVZ, and are recommended for people who either need the additional capability that a non-oversold node will have or want the improved reliability.

The third one that is only barely mentioned most of the time is KVM. It's similar to QEMU, and like Xen provides a full isolation between host and guest. Although I am not certain on this, KVM very likely is similar to Xen in that the RAM is allocated when the VPS is started, and cannot be easily oversold. A growing number of providers offer KVM based VPSs though because of the ease of using any OS you like with them, even Windows can run out of the box in a KVM VPS.

[wswd]

Although I am not certain on this, KVM very likely is similar to Xen in that the RAM is allocated when the VPS is started, and cannot be easily oversold.

KVM is actually very easily oversold, like OpenVZ. Though there have been certain stability issues on oversold KVM servers.

[JamesZach]

I would go for xen virtulization because its resembles more to an actual dedicated server. From a customer perspective i would go for xen because i would know that my resources are dedicated.