Mailing List Archive: domU snaphots

I'd like to snapshot a domU at any time to have a checkpoint of the
domain.

Actually I only need the partitions saved, not the domU.

I'd do this now by shuting down the domain, hence the fs are umounted and
then dd/partimage the partitions.

its not perfect, because I have around one minute downtime and actually
a shutdown.

If I see the xen migrate/save of a domain, why not copy the domain with its
disks ?

Is

- xm pause ..
- xm save ..
- dump saved_domU and its disks to a checkpoint
- xm unpause
- restore the checkpoint, shut it down and dump the disks

an option, or how would you do that ?

marcel

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> If I see the xen migrate/save of a domain, why not copy the
> domain with its disks ?

It easy to add this functionality, and its on the todo list.

Because of the live migrate code in xc_linux_save, it will be possible
to take a checkpoint of a domain without actually stopping it (well,
probably not for more than a few 10s of ms).

The only difficulty (which is why we haven't done it yet) is that it
requires a bit of co-ordination with LVM to create a snapshot of the
VM's file system at the synchronization point. This require a bit of
xend hacking to invoke LVM at the appropriate point. No more than a
couple of hours work for someone that knows xend.
(It's probably best to have xm checkpoint receive the name of the LVM
volume it should snapshot the filesystem to on the command line, to
avoid having to worry about allocaitng one).

Ian

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