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 B & C are still valid IIUC, this is how VMWare works & we essentially need our API to map to that since VirtualBox seems to follow the VMWare model too & there's no reason that QEMU can't too. Daniel -- |: Red Hat, Engineering, London -o- http://people.redhat.com/berrange/ :| |: http://libvirt.org -o- http://virt-manager.org -o- http://deltacloud.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: GnuPG: 7D3B9505 -o- F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 :|