Re: [Xen-users] xm save -c

["Mike Sun" <msun@xxxxxxxxxx>]

Hi Nick,

> I was wondering if anyone knows of a way to "checkpoint" without pausing the
> domain?  I can't do something like an hourly checkpoint if the domain pauses
> every hour - the users on the domUs would kill me.  Is "seamless
> checkpointing" something that's being developed, something that can be done
> another way, or something I should just give up on now?

I've been working on something for my research that probably addresses
what you're looking for: low latency/downtime checkpointing.  There
are two ways I know this can be done.

You can modify the live-migration mechanism in Xen to save a
checkpoint instead of migrating to another host.  I don't know why
this hasn't been provided in the xm save tool, but it's a pretty
simple hack to get working since the xm migrate and xm save codebase
is basically the same.  If you're interested, I can send patches to
allow you to do that.  Then basically on a checkpoint, pre-copying
would be used to cut the actual time the domU has to be paused.

The other way that I've implemented for my research project is to use
copy-on-write.  I've implemented a prototype and in the middle of
writing paper for publication.  It's not suited for production use,
but I'd be glad to contribute the code if there's interest.

Mike

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