Re: [libvirt] [RFC PATCH 1/n] snapshot: add revert-and-create branching of external snapshots

On 11/14/2012 04:33 AM, Guannan Ren wrote: Right now, I'm only proposing the ability to branch from an external snapshot (whether disk-only or external checkpoint doesn't matter). So you are indeed correct that if I have used snapshot commands to create external snapshots leading to the chain: base <- snap1 <- snap2 and then request a revert-and-create of snap1.1 with snap1 as the branch point, then I will have: base <- snap1 <- snap2 \- snap1.1 with snap1.qcow2 and snap1.1.qcow2 BOTH having base as their backing file, but with the two files diverging in contents based on what the guest has executed in the meantime. Then, I'm also proposing a new operation for plain revert, which says to revert to the external snapshot PLUS its subsequent disk changes, which will let me pivot between the two branches by altering which qcow2 file we load when booting the guest. We are not booting up the guest before creating the new snapshot. The new branched snapshot shares the same BASE files as the branch point. The parent of the branch snapshot is the same parent of the original snapshot we reverted to - not the reverted snapshot itself. -- Eric Blake eblake(a)redhat.com +1-919-301-3266 Libvirt virtualization library http://libvirt.org