On 09/13/2012 08:56 PM, Eric Blake wrote: > On 09/13/2012 02:59 AM, Kashyap Chamarthy wrote: >> Hi (Eric?), >> >> A couple of questions while using the 'virsh blockpull' >> >> >> >> Summary: >> >> 1] Created snapshots this way: base<-snap1<-snap2<-snap3 (online, external snapshot >> --disk-only) >> 2] I did a 'virsh blockpull' from snap2 into snap3 >> 3] Next, did another 'virsh blockpull' from snap1 into snap3 > > You could have also done a 'virsh blockpull' from snap1 into snap3 > without the intermediate pull of snap2, but shouldn't make a difference > to your end question. > >> - Here, 'qemu-img info /path/to/snap3' shows its backing file correctly as snap1. But not >> 'virsh snapshot-list $domain --tree' . Any hints? > > virsh snapshot-list is still accurately listing the state of the tree at > the time of the snapshot, OK. > not what you have done after the snapshot. If > you were to revert to snap1 or snap2 (assuming that I ever get > revert-to-disk-snapshots working), Um, till 'revert' is implemented, I'd assume, the existing use-cases with 'external-disk/live' snapshots would be the ability to manage/manipulate the backing chain. Or take the guest offline and do the snapshot-manipulation with 'qemu-img' > you would still be able to do that, > provided you haven't deleted snap1 or snap2 from your file system. That > is, it is feasible to go from: > > base<-snap123 (snap1 and snap2 were pulled into snap3) > > and then revert back to: > > base<-snap1 (undo the changes that were in snap2 and snap3) > > Libvirt does not modify any snapshot information when doing a blockpull > operation, and I'm not yet convinced that it even needs to. (I'm > dreading if it does, because having a blockpull update the snapshot tree > seems rather complicated.) Agreed. As is, the differentiation between 'snapshot chain' and 'backing chain' can be easily missed(like I did) if not closely observed. > >> >> Here, shouldn't 'virsh snapshot-list' --tree be updated as well ?(since 'snap2' is no more >> the backing file for 'snap3' ?) > > The snapshot chain is independent of each disk's backing chain. This is the point, I should have had more clarity about. > The > snapshot chain is still correct, because you haven't used 'virsh > snapshot-delete' to shorten the snapshot chain (then again, I still > haven't implemented that for disk snapshots...) Noted. Thanks, for your lucid responses(as usual). Also, when you have a moment, can you please differentiate between 'blockcopy' and 'blockpull' /me is reading the 'virsh' man page for the details, but a bit more explanation about what scenarios it'd be useful will help clarify things while I'm experimenting with them. > -- /kashyap _______________________________________________ libvirt-users mailing list libvirt-users@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvirt-users
