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VE checkpointing/migration is released

We have just pushed the kernel checkpointing stuff to git.openvz.org. That means the code is now available, and this is what I consider major news. Kernel and tools will be released shortly.

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.

Imagine you want to add more RAM into your (physical) server, or upgrade the kernel. Such operations require a reboot of the physical server — means you have to shutdown all your VEs. But now you do not need to do that — instead you live migrate all VEs to another OpenVZ box, when do that maintenance and live migrate VEs back. From user's point of view, this looks like a delay in processing, not as any downtime. All the network connections and all the other stuff is preserved — that is why it is called "live" migration.

Another scenario is when your VE has grown considerably and it needs more CPUs than the server has. Again, you put another server with OpenVZ installed, and live migrate your VE to it. No hassles, no reconfiguration, no downtime.

Isn't it amazing? Yes it is. The most amazing thing though is the technology itself is free software. Free as in freedom, not as in beer, please do not mix those.


( 2 comments — Leave a comment )
Apr. 19th, 2006 11:02 pm (UTC)
Thank you (or whoever is responsible) for adding this to OpenVZ.

I have a remote box that is a couple of thousand miles away. I hope the transition to the new kernel/tools will be painless. I'll surely test this out on a few local boxes first... once the binary/rpm packages are released!

So, where might one find some documentation for this? Will the OpenVZ User's Guide be updated?
Apr. 20th, 2006 03:51 pm (UTC)
Re: Fantastic
RPMS are already released. There is not many new docs, since from the user's point of view it's quite simple.

There is a man page for the new vzmigrate utility, and an addition to the vzctl man page which describes new 'chkpnt' and 'restore' commands.

Apparently vzmigrate man page was slipped from vzctl release, so it is available only on the web site and in git repo...we will fix it in the next release.
( 2 comments — Leave a comment )

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