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Re: [Xen-devel] Domain save/migrate issue

To: veillard@xxxxxxxxxx
Subject: Re: [Xen-devel] Domain save/migrate issue
From: Steven Hand <Steven.Hand@xxxxxxxxxxxx>
Date: Tue, 14 Feb 2006 14:44:29 +0000
Cc: Noam Taich <noam.taich@xxxxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx
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In-reply-to: Message from Daniel Veillard <veillard@xxxxxxxxxx> of "Tue, 14 Feb 2006 09:41:49 EST." <20060214144149.GE9506@xxxxxxxxxx>
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> On Tue, Feb 14, 2006 at 06:08:06AM -0800, Noam Taich wrote:
> > As it stands now, when a domain is saved to disk it is suspended in the
> > process, and then destroyed. This is done by the checkpointing code in
> > Xend.
> > However, it's a good idea to leave the option open to the user whether
> > or not the saved domain should be kept alive or be suspended,
> > as it is very possible this feature may be used in real checkpointing of
> > a working domain state, just in order to not lose everything should
> > something go wrong.
> > 
> > if you have a guest which does some heavy calculations, or one which
> > handles many customer's connection this may be a good idea even in
> > migration (which calls the checkpointing code anyway.), although in the
> > latter case, of course the network interfaces of the new domain will be
> > taken down, and it may be used as a hot spare ready for a quick
> > hook-up...
> > 
> > So what do you think?
>   I tend to agree, it's about having orthogonal APIs, I think you can build
> the current behaviour by a sequence of the simpler save and a destroy (though
> it would not be atomic anymore). Is there any strong reason a saved domain
> must not be left running ?

Unless you also have some way to simulataneously snapshot the file
system, it is not safe to allow the guest to continue and then later
resume the checkpointed version. 


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