Re: [libvirt] [RFC]: Snapshot API

2010/3/24 Daniel P. Berrange <berrange(a)redhat.com&gt;: > On Wed, Mar 24, 2010 at 09:09:08AM -0400, Chris Lalancette wrote: >> On 03/24/2010 04:52 AM, Paolo Bonzini wrote: >> >> > >> >> > How can<parent>  be settable? If I have snapshots A and B >> >> > >> >> >    A ->  B ->  current state >> >> > >> >> > and I create a new snapshot C, then B will be the parent of C. >> >> > >> >> >    A ->  B ->  C ->  current state >> >> > >> >> > If I create another snapshot D now and specify A to be its parent, >> >> > what's supposed to happen then? >> >> >> >> You are right, that doesn't make that much sense.  I have to admit that >> >> the tree structure is the part I thought about least, so I'll take that >> >> part back. <parent> is just going to be an informational field about >> >> which snapshot was current (if any) when this one was created. >> > >> > If discarding a snapshot also discards the children, it would definitely >> > make sense to be able to specify the parent. >> >> The problem, though, is what Mattias points out; there is no (easy) way >> that, given state C, I can get back to state A to make a new snapshot. >> I actually have to be at state A to take a new snapshot with a parent of >> A.  I think this is a place where we have to make it manual; if you really >> want a new snapshot that is a child of A, you'll have to manually shutdown >> your domain, boot to snapshot A, then take a snapshot of A. > > This is something virDomainCreateAtSnapshot() should solve. > > If you have a series > >   A -> B -> C > > And you do  virDomainCreateAtSnapshot(dom, "A"), then you get 'D' > >   A -> B -> C >   | >   \-> D You mean you get D when you do a virDomainSnapshotCreateXML(dom, NULL) _after_ you've done a virDomainCreateAtSnapshot(dom, "A"), don't you?