[libvirt] [patch 0/4] checkpoint functionality

[Daniel Veillard]

On Mon, Mar 09, 2009 at 11:14:56PM +0900, Matt McCowan wrote:
> OK. Another run at producing a function that helps the likes of me
> backup my kvm Windows servers.
> 'virsh checkpoint domain file [script]' is what the following patch set
> (against cvs) enables. Modelled on the virDomainSave function it takes
> an optional script which it will execute (and pass the name of the
> domain as an argument) while the domain is paused, then resume the
> domain.

  Okay, I quickly looked at the patch and the new API, so no stylistic
review at this point but more a general feedback. I appreciate the
completeness of the patch (only bit missing is filling up the virsh
man page with the new option)
  I think this can help administrators in a controlled situation,
but I'm hoping a real snapshotting API will be possible at some point
where libvirt goes though the list of storage resources used by the
domain and properly make a snapshot using a storage API or return
an error if that's not possible.
  This looks more as a script extension to virDomainSave/Restore
than really a snapshotting API as I would like libvirt to get at some
point. To me it doesn't implement snapshotting, it implement running a
script on a frozen domain. There is a lot of issues with that:
  - the script need to be in place and there is no hint of what
    it may contain
  - what the script does is unbounded, there is a potential very
    serious security issue there
  - this does not garantee sucess of the operation and in case of
    failure the script can't even propagate back an error code and
    description

  In my opinion this is a bit too ad-hoc to be turned into a full API
maintained forever, and I'm worried about remote execution capabilities
this opens up. I really hope we will have one day a real checkpointing
API in libvirt, but that requires making more progresses on the storage
management side.
  Still thanks for sending the patches, even if I think this is not ripe
for inclusion, it reminds us that snapshotting is a big issue and need
to be taken care of !

> By the by stability is coming along nicely since 0.6.0. Thanks!

  Yeah, there were a lot of changes, and bugs are ironed out
progressively. Check the version from CVS/git/snapshot to get the
latest changes as usual,

Daniel

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