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Xen VPS vs OpenVZ

 

OpenVZ is an open source variant of the proprietory virtualization solution Virtuozzo. Timewise, openVZ appeared earlier than Xen. OpenVZ is widely used for Virtual private servers (VPS) by hosting providers and once was the dominant solution.

Xen is a different type of virtualization developed later and which is free of most of openVZ's problems and shortcomings.

In the table below we tried to summarize the differences between the two types of virtualization.

 

openVZ

Xen

One kernel serving all VPS within the host server.

 

1 single kernel = less stability. The kernel serves many VPS and the processes they generate.

Dedicated kernels for each VPS on the host server

 

Dedicated kernels = more stability, independent environment.

To load a custom kernel module you need to ask the hosting-provider to do so

Full user control over loaded / unloaded kernel modules

Only Linux-based OS can be installed as the OS on the VPS

Any OS can be installed on the VPS, even Windows

Shared filesystem (disk).

 

Filesystem failure will affect all VPS located on the server.

Dedicated separate filesystem.

 

Filesystem failure for one VPS doesn't affect the other VPS hosted on the server.

Resources (RAM, CPU) are allocated by software "counters" that prevent using them over the limit declared in the VPS plan.

"Honest" resource allocation.

RAM shortage possible.

If a VPS's scripts use RAM more efficiently, the other hosted VPS may experience lack of memory.

Every VPS uses only the part of RAM that has been allocated to it and uses it the way a real server does.

Changing resource allocation (CPU, RAM) doesn't require a server reboot.

Changing resource allocation (CPU, RAM) requires a server reboot.


Thus, the disadvantages of openVZ make it resemble shared hosting. However, openVZ VPS are undoubtebly more performant than shared hosting. But less stable than Xen VPS which are probably the best choice for a VPS.