On Wed, Feb 11, 2015 at 5:09 PM, Eric Blake <ebl...@redhat.com> wrote:
> [dropping multiple lists; let's just use libvirt-users] > > On 02/11/2015 02:45 PM, Edward Young wrote: > > > I perform a simple test, but failed. > > > > In the source, I create: base <- mid <- active (2 snapshots, the active > > one is the current one) > > In order to migrate this vm to the destination, I manually copy both base > > and mid to the destination, and put them in the sam e directory > > /var/lib/libvirt/images/ > > Then I call the following commands: > > 'sudo virsh migrate --live --unsafe --verbose --copy-storage-inc vm1 > > qemu+ssh://192.168.1.3/system tcp://192.168.1.3' > > > > The error I got is: > > error: Requested operation is not valid: cannot migrate domain with 2 > > snapshots. > > > > I do not know the reason for this. > > That's because libvirt is not (yet) able to migrate snapshots in a way > that the destination can revert to them. It is possible to work around > this in a couple of ways: > > 1. Manually dump all the snapshot XML configurations on the source side > (virsh snapshot-list, then virsh snapshot-dumpxml in a loop), then > delete the snapshot tracking (virsh snapshot-delete --metadata in a > loop), then do the migration, then manually recreate the snapshot > configuration on the destination (virsh snapshot-create --redefine in a > loop for each of the xml files you saved earlier). > > If you don't plan to revert to snapshots on the destination, then you > can skip the snapshot-dumpxml loop, as well as the snapshot-create > --redefine loop. But if that's the case, then you can take a shortcut: > > 2. Don't track external snapshot data in libvirt in the first place > (virsh snapshot-create --no-metadata when taking external snapshots). > Instead, the backing chain is sufficient to know that external snapshot > data was saved. > It works for me. Thanks! > > > > > > >> In fact, modern > >> libvirt/qemu does this for you by setting up an NBD server on the > >> destination, doing a data mirror from the source into the destination > >> (so that you DO have shared storage, at least for the duration of the > >> migration), then doing the live migration, then tearing down the NBD > >> mirroring link. > >> > > > > Sounds interesting! Can you provide me an example or point me to a link > > about how to use this function? > > It's all done under the hood as part of the implementation of 'virsh > migrate --copy-source-*', if done as part of migration. But if you want > to manually recreate the steps, the source code in > src/qemu/qemu_migration.c shows the QMP commands used to set up the NBD > server on the destination, then the mirroring is done with equivalent of > the 'virsh blockcopy' command pointing to the NBD server as the > destination. > I will take a look at the code. > > > > > Sorry to take you so much time to answer my questions. I appreciate it > > deeply. After I solve this issue, I will write a blog and share these > > knowledge with other people. > > The libvirt-users list archives has a lot of questions and posts from > other users on the same topic; it may also help if you peruse the archives. > I tried previously, but I can't find them. I search them directly by google? Is there anyway to find the related posts in the archive? Thanks a lot! Ed > > -- > Eric Blake eblake redhat com +1-919-301-3266 > Libvirt virtualization library http://libvirt.org > >
_______________________________________________ libvirt-users mailing list libvirt-users@redhat.com https://www.redhat.com/mailman/listinfo/libvirt-users
