KVM, OpenVZ or Xen, which is better?

Started by samfrank, Jul 06, 2022, 12:53 AM

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samfrankTopic starter

From the point of view of a VPS client, which virtualization is more resource-fair - KVM, OpenVZ or Xen?


I will definitely say NO for OpenVZ. Because this technology does not provide  resource control flexibility.
OpenVZ allows you to host more "guests" on a physical server, which reduces the cost of user. But worse quality.

It's harder to choose between Xen and KVM. Both technologies allow you to run real operating systems with a lot of freedom for the user.

Xen paravirtualization to run Linux would be, in my opinion, more reliable, faster, and more predictable than KVM.

For running virtual machines using hardware virtualization, like running Windows or FreeBSD, I trend towards KVM.

Everything depends of the tasks.
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Lucas Babcock

OpenVZ is the smallest size and therefore the most cost-effective, but keep in mind that the market for these systems is the smallest (I mean limited to Linux VMs only), and therefore the most inefficient (market demand). From this, we can conclude that such a system cannot be considered low-cost. Many Xen systems are paid (like Xen itself), so in terms of spending money, it is the most wasteful.
What remains is Linux KVM, which performs well both in terms of comic resources and in technical terms (full virtualization).


In general, a lot depends on the hoster, if you do not sin with overselling on OpenVZ, then this is practically the same level of quality with Xen, and if you consider that IO performance is lower on Xen, then maybe he also wins.
Another question is that most hosters, in order to reduce the price, oversell on OpenVZ, and here of course Xen looks more stable.


KVM provides full hardware virtualization. In essence, that means that you can run any operating system as a guest, be it Linux/Windows/BSD, and together with the virtual driver you get almost identical native performance.
It supports installation based on ISO and templates. It also has a good separation in terms of privacy, since the data is hidden from other users. However, under heavy load, the I/O log may sometimes occur, which may affect the host operating system and guest operating systems.

KVM uses hardware virtualization technology, which means that the main operating system on the web server can simulate hardware for another OS to run on top of it. It then also acts as a hypervisor that manages and allocates shared resources such as CPU time and network I/O.

KVM does not contain batch resources, all of them are either shared or allocated. This means that the entire disk space or RAM is usually more difficult to overload, since there is an imminent danger to all user data.
The downside of KVM is that if resources exceed the limit, the VPS must swap places, which can lead to a serious drop in performance or start destroying processes one by one. Unlike OpenVZ, KVM cannot temporarily operate by borrowing funds from one of its partners, since all allocated resources are completely isolated from each other.

OpenVZ is becoming increasingly popular in the web hosting industry due to its very high density and rapid deployment. This is possible because the host kernel shares disk space, CPU, and RAM with the guests. There is a very simple separation between host and guest, and there is practically no I/O bottleneck.

OpenVZ is a virtualization software offered by SWsoft Inc. OpenVZ offers a huge number of advantages for the administrator, because it allows you to host multiple virtual environments on the same server. The only limitations for that are CPU and RAM.

OpenVZ is an OS—level virtualization technology based on the Linux kernel. This allows a single physical web  server to run several different instances of the operating system, known as virtual environments or virtual private servers.

Unlike paravirtualization and VMware technologies such as Xen, OpenVZ is limited because it requires both the guest and host OS to be Linux, although Linux distributions may be different in virtual environments with a common core. OpenVZ offers a good performance advantage, and the penalty for running OpenZ is 1 to 3% compared to another standalone web server.

Xen is an open source hypervisor included in the Linux kernel, so it can be found in all Linux distributions. The Xen Project is one of many projects distributed and managed by the Linux Foundation.

The environment in which Xen works can consist of different parts. Initially, there is a domain 0. In Xen, that is a way of designating the host operating system (OS), since it is not, in fact, the host operating system, since it is not available to other virtual machines to access the host web server hardware. Domain 0 is only responsible for providing access to drivers and maintaining the coordination necessary to run applications. In addition to domain 0, there are other virtual machines called domain U.

Xen offers two different types of virtualization: paravirtualization and full virtualization. During paravirtualization, the virtualized operating system runs a modified version of the same OS, as a result of which the main OS knows that it is virtualized.
This ensures efficient and effective communication between the physical hardware and the OS, since all hardware devices can be connected directly. The only real disadvantage of paravirtualization is that it requires a modified guest OS that is not supported by a number of vendors.