Many have asked which type of VPS to choose and what are the difference? The propose of this post is to help customer to make the right choice. It is not because Vastspace have dropped OpenVZ and we start praising KVM. Vastspace has dropped OpenVZ is base on demand and it is difficult to manage 2 types of virtualization at the same time., Finally we have chosen KVM instead.
We are not saying OpenVZ is bad. Honestly, there are many advantages for hosting vendors like us. Hosting providers can put more instances on one node compares to KVM. As you know OpenVZ is sharing files and kernel. Theoretically, you are using less space or space is available to you dynamically. Even you are given 40 Gb of space but OpenVZ is calculating the space only you are consuming and not allocated.
Because OpenVZ is sharing the node kernel, you cannot reboot the virtualized instance at your own. In other words, you cannot update a kernel bug or security fix. This has to be waited till the virtualization distribution released and schedule to be updated as a whole but not individually.
OpenVZ allows the use of memory does not belong to you or has been allocated to you. There is mean to say, if you are allocated with 1Gb of RAM you might be able to use more. If you look at other angle, you are stealing others RAM. What happen if someone is stealing from you? This will only happen to unused RAM. In many occasions, RAM is taken from the node and the entire server freezes because of overage. All the VPS hosted within the server are affected due to poor management and this will not happen to KVM. However, there are much improvements in virtualization, there is such thing know as burstable memory, this can be done on KVM VPS.
There are some applications required non-shared kernel. For example, a real-time anti-virus which is essential for today cyber world, can only install on a KVM VPS and not OpenVZ VPS due to its shared kernel.
In real world, CPU are shared in OpenVZ . CPU are dynamically shared among the client machine. You can say it is burstable unlike KVM, you only can use what is allocated to you. because of this feature, it has allow more instances to be hosted. In other words, it is cheaper per instance on OpenVZ.
These explained the difference between OpenVZ and KVM virtualization Hope that the article helped you to make a better choice in choosing a VPS.