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KVM vs OpenVZ. Which Virtual Private Server Virtualization is Best for You?

There are many Virtualization software’s – VMware, Microsoft Hyper-V, Virtuozzo/OpenZV, Parallels, Citrix XenServer, KVM, & SolusVM – out there to choose from, but for this article, we are going to focus on two of the most popular ones that are in use in most production systems.

“KVM vs OpenVZ, which virtualization is better for me” is a question that comes up often when a client is looking into a VPS, Virtual Private Server. Once you have compared RAM and disk space specs, take a look into which virtualization web hosts offer.

OpenVZ vs KVM

First of all, the most basic difference between OpenVZ and KVM is that OpenVZ can only host Linux operating systems, while KVM is more flexible and can host Linux, Windows, and custom OS options.

Both a good and bad of OpenVZ is the complete sharing of resources it allows. OpenVZ uses a shared kernel with a layer of virtualization on top of the actual Linux OS. Since this kernel is shared by all VPS users on the node, the kernel is not customizable. Once you have hit your allocated RAM provided to you by the host, the remaining RAM becomes a free for all for users on the server. This is not a problem if you run small applications, but you may be in trouble if you are running something more resource intensive.

KVM allows you to set maximum and minimum values to your resources, so that you only use the resources your applications need. This is real hardware virtualization, meaning better performance from lower requirements on the hypervisor. 100% of the RAM and disk resources are dedicated to one individual user. KVM provides a more isolated environment and gives users their own kernel.

The risk of overselling has been a recurring problem for some time, but then again, server hardware can get seriously expensive depending on the ordered configuration. Overselling is where a host will over commit resources to certain accounts hoping that not every account uses up all those resources. While everything can be oversold, beware of shady hosting companies over committing OpenVZ systems and putting you on a system with too many containers. KVM can also be oversold, but it’s better isolated. Since OpenVZ hosts are often oversold, OpenVZ servers are typically a cheaper cost than KVM servers.

OpenVZ provides the end user with speed and scaleability, and it’s more affordable. KVM offers private virtualized hardware including network card, disk and graphics adapter, and guaranteed resources for increased reliability and customization. KVM packages are ideal for serious resellers, game servers, small businesses, and medium sized enterprises.

If you are a host selling to your clients, OpenVZ is easier to set-up and maintain properly, while KVM takes much more networking knowledge. OpenVZ and their templates are more beginner friendly in that aspect. If you are simply an end user, don’t worry and go with a managed infrastructure provider.