Quoting from the OpenVZ blog:
We have just pushed the kernel checkpointing stuff to git.openvz.org.
…
It’s a huge pile of code that lets you checkpoint your virtual environments — in the same way you do “suspend to disk” or “hibernation” on your laptop. This is cool, but what’s the use of it for VE? Here it is: you can actually restore (“wake up”) a VE on a different machine! The process is called live migration; newer vzctl will have a tool called vzmigrate for that…
Read the whole article at source.