OpenVZ, KVM and Cloud VPS Servers - What is the best virtualisation technology to use?
If you are in the market for a VPS hosting you may have a hard time choosing between the many different platforms and options out there. Even at VpsCity we offer three different options OpenVZ, KVM and Cloud VPS hosting. Each with a different price point and unique advantages/disadvantages.
OpenVZ: User-Friendly Linux based VPS Containers
This is an OS-level virtualisation in which the kernel is used to split the OS into partitions called containers. The kernel itself is shared among several VPS. OpenVz can only run Linux based operating systems such as Centos, Fedora, Gentoo, and Debian.
Resources in OpenVZ are divided into two, dedicated and burst resources. The dedicated resources are what a VPS is guaranteed to get whenever they demand them. Burst resources, on the other hand, are those available from unused capacity in the system. This form of virtualisation allows one VPS to borrow or use resources belonging to another VPS which are not being used. Burst resources can help you meet a short-term need for more resources. However, should they become needed, your process may become unstable or even terminated. The biggest advantage of OpenVZ is its efficient use of resources. It makes significant memory and CPU savings. At the same time, it results in higher performance since it does not run a full virtualisation emulation and on different kernels at that.
Other advantages include its simplicity to set up, use and manage. It is also the most affordable per VPS container.
The disadvantages start from the lack of flexibility it has. It is restricted to the Linux OS only limiting its features. It is also impossible to customise your VPS configuration. There is also the risk that should a shared kernel fail, all the VPS instances running on the same server will be affected.
KVM: Customise your service to suit your needs
KVM which is an acronym for Kernel-based Virtual Machine is a hardware virtualisation technology built on Linux Core. However, it also allows you to run another kernel on the root node. This makes it possible to run other OS on KVM like Windows and BSD. This is possible because this technology mimics real hardware. As a true hardware virtualisation machine, KVM offers some amount of control among the users. You get to set the maximum and minimum values for your resources allowing you to use only the resources needed by your applications. The hypervisor is what fairly distributes shared resources among all users in the virtual environment. Shared resources include network IO, disk space and CPU time. KVM offers more degree of isolation since each user owns their kernel. It is the closest to a dedicated server one can get presently.
The advantages provided by a KVM VPS include the ability to work with any other OS. This makes it even easier to enjoy hidden features not supported in OpenVZ. By allowing custom kernels, it makes it possible for you to upgrade your software without reinstallation. It also has the advantage of meeting heavy user demands since you get a lot of resources to work with and an almost dedicated server to meet your demands. For a host, KVM demands higher overhead costs.
The next two platforms can be grouped into the same category as KVM because they work almost identically. Both platforms provide true virtualisation resources and are not shared between the host kernel or other virtual servers. Almost any operating system can run on both platforms. We choose to use the KVM platform because it supported by the Centos operating system that we use as the host OS.
Cloud is the new term companies large and small are kicking around. There is no true definition on what a cloud is or how it is supposed to be designed. And in our opinion the term "cloud" that applies to VPS hosting is no different than a VPS that has failover, redundancy or backup. So coining the new term "cloud" and the extra hype is completely not necessary. A typical cloud setup runs on the KVM, XEN, or VMware platform. The difference is on the type of hardware that is used. Instead of having storage located on the host server all data is stored on a much larger SAN/NAS array with multiple disks. Raid is used to prevent disk failure on the physical array and in the best case scenario, a second array is added in case the entire array fails. The host server accesses the storage via fibre. In the event of a host server failure spare host servers are on standby to startup when needed. Downtime during the failure would be a reboot of your operating system. At VpsCity our cloud setup runs on the KVM platform with two storage arrays. The advantage of cloud is a truly redundant environment. All aspects of hardware failure are 100% covered.
Our cloud hosting is supported by the high-availability system we have developed. This system ensures that your virtual server will be automatically taken over by another one in case the primary virtual server encounters problems.