PC virtualization mainstream: KVM, XEN, OpenVZ Detailed
https://zhuanlan.zhihu.com/p/90920566
1, pc virtualization --KVM
KVM is a full virtualization of hardware, operating systems can be run perfectly in Windows / Linux, and uses virtio drivers can get near-native performance, some experiments show that, in the ideal case the loss of native hardware is only 3%.
It does support installing from ISO, also supports mounting template, with good isolation in privacy, would suffer under a heavy load I / O latency.
Each user (VM) both as a process running on the host node, which is very suitable for the user to identify problems which occur at run time, all users if the hosts are under a heavy load to bear, as long as the user load caused by the closure of the source of the problem can be solved
You can not consider the allocation of Ram, but in most cases, unless the host is complete SSD hard drive, or to do so the user experience is poor.
Since KVM is the most modern kernels native, in some cases, it does have performance advantages over other kernel, and still fairly new, and is in very active development.
Most people choose KVM is to obtain excellent performance and flexibility, although due to the maturity of Xen may not be as stable.
2, pc virtualization --XEN
There are two versions of Xen, but (paravirtualization) on the same physical host Xen PV and HVM (complete hardware virtualization) running simultaneously
Xen PV guest virtual machine (in the hosting industry) tend to template-based, in order to achieve rapid deployment and fast performance, you can run your own kernel Xen PV in.
Xen HVM and KVM operation mode is very similar, it has better drivers based on Linux distributions, because since around 2006 began to provide most PV kernel by default, so you do not need to improve server performance installation virtio, but and KVM, although you can use the Xen PV drivers on Windows, but still better than the overall KVM poor part of it.
Xen is now very mature, most people choose to get Xen outstanding performance with excellent stability.
Xen host will usually Ram and CPU cores pre-assigned to the xen hypervisor, so it has its own dedicated resources, users can not influence to achieve stability.
3, pc virtualization --OpenVZ
OpenVZ due to its rapid deployment and a very high density and popular in the hosting industry, it can achieve this, because the host kernel ram, cpu and disk share together with the guest, and the guest and host I / O between the partition bottleneck fairly basic almost non-existent.
Compared with KVM and Xen, on disk and disk access speed in terms of delay, OpenVZ is clearly the winner, but at the expense of the lack of resolution, but also a lack of influence on both OS users. And other users host node, the host node for all the individual processes are visible, and you can not encrypt data.
OpenVZ supports only Linux (unless commercial parallel use will support Windows in some way)
OpenVZ may be nested within Xen or KVM to achieve greater density, due to the large number of containers that can be run on a single host node, which makes the price competitive with OpenVZ KVM and Xen.
Summary: OpenVZ is easy to configure and get started. Further, since it is a container system, so the OpenVZ much less expensive, so the provider may configure more from a single physical server VPS. OpenVZ compared to the previous two kinds have the biggest ills, using the host virtualization technology providers such overbooking is often very serious, serious almost unimaginable. You may buy hosts started running very smooth, but a period of time all kinds of weird problem occurs, probably due to overbooking host provider.
There is no lack of conscience manufacturers no overbooking, if you can focus on interest virtualization " technology which is better cloud server host virtualization? What are the advantages and disadvantages? "Learn more about.