KVM Or OpenVZ For VPS?

What is the best choice of VPS with low end RAM, say 128-256MB? Well the answer is it depends! KVM offers much better isolation than OpenVZ, but for basic web hosting, or hosting wordpress blogs, this might not matter too much. OpenVZ is an opens source operating system level virtualisation technology developed by Parallels. KVM stands for “Kernel Based Virtual Machine” and was developed originally by start up Qumranet, eventually bought out by Red Hat.

Because KVM requires a running kernel within the container, it should in theory require more overhead, than OpenVZ, which is basically OS level virtualisation. As such OpenVZ is limited to running purely Linux environments. KVM can boot and run Linux, Windows etc on the same hardware.

As OpenVZ shares a kernel amongst all the containers I can’t see how the performance can be worse than KVM. This should allow more memory for userspace. Indeed OpenVZ is an extremely lightweight virtualization technology that easily outperforms full virtualization. KVM, Xen and so on, will however provide more of a “dedicated server” kind of experience, with the ability to load kernel modules and so on. For most hosting applications this isn’t often neccessary, but has its uses when setting VPN’s and tunnelling and so on.

The other issue with OpenVZ however is that the memory allocation per container is quite complex and some hosts rarely get this right. This might result in you not quite getting the memory or burst ram you required. Also the configuration for OpenVZ makes it very easy to oversell resources, in the form of RAM and disc space.

For basic llinux web hosting, OpenVZ is fine, just choose your  provider carefully and ask for config of the plan you are signing up for and research the hardware and amount of contention (number of VPS’s per node). If you require kernel access and more of a dedicated server “feel” or even Windows hosting, then opt for KVM