Dear Eric, Thanks for your tips and explanations.
I think there will be lots of works to do. And I migrate VM with snapshot successfully by your tips. Thank you so much. I am really appreciated. Hubert On Thu, Mar 21, 2013 at 11:40 AM, Eric Blake <ebl...@redhat.com> wrote: > On 03/20/2013 08:45 PM, Chiang Hubert wrote: > > Hello, > > > > I'd like to live migration with snapshots. > > > > But it doesn't work. It comes out a message "cannot migrate domain with 1 > > snapshots" > > Unfortunately, figuring out how to migrate snapshot information at the > libvirt API level requires some engineering work - the current RPC > protocol for migration is not set up to migrate an arbitrary amount of > snapshots in a single call. > > On the other hand, if you are allowed to make more than one API call, > the solution is already available; maybe we should patch virsh to learn > how to make the series of API calls, to automate what I will describe > below. > > > > > Then I try to trace the code(Libvirt 0.9.8 to 1.0.3), I find out the code > > in src/qemu/qemu_migration.c @ Line 1395 - 1440 (Libvirt 1.0.3) > > It's still unimplemented at the libvirt level, even in libvirt.git. > > > > > It will check the VM which has snapshots or not. > > > > I just curious about this limitation, why the VM can't live migration > with > > snapshots? > > Doing it all in one RPC call would be a potential denial-of-service > (RPCs are bounded in length to avoid consuming server resources, and > taking lots of snapshots on the source could easily be made to exceed > bounds). If someone can design a way to set up a series of RPC > handshakes, then we could do it at the libvirt level in a single API > call, but I'm not sure it is worth it. > > > > > What happen if I skip this check? > > > > Does it has any suggestion way or virsh command with options to do live > > migration with snapshots? > > The existing solution at the management tool layer is to migrate the > snapshot information first, and then to migrate the domain. For each > snapshot in 'virsh snapshot-list --name $dom', you will want to 'virsh > snapshot-dumpxml $dom $name > file' on the source, then 'virsh > snapshot-create --redefine $dom file' on the destination. Next, > determine 'virsh snapshot-current --name $dom' on the source, and use > 'virsh snapshot-current $dom $name' on the destination to set it as > current (if there is a current snapshot). After the destination has all > the snapshots, you then loop over 'virsh snapshot-delete --metadata $dom > $name' on the source, at which point, live migration will now work. > > Patches to teach virsh how to do all this work in a single 'virsh > migrate' are welcome. > > -- > Eric Blake eblake redhat com +1-919-301-3266 > Libvirt virtualization library http://libvirt.org > >
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