[libvirt-users] Migrating guests

[Kashyap Chamarthy]

On Thu, Jun 11, 2015 at 07:28:10PM +0200, Dominique Ramaekers wrote:
> Hi,
> 
> I'm experimenting with the migration function of virsh. I'm doing the
> migrate with following commands:
> 
> virsh migrate --life --persistent --copy-storage-all --verbose
> --abort-on-error domain qemu+ssh://root@destination/system virsh
> migrate-setmaxdowntime domain 20000
> 
> However sometimes at the end of the migration, the guest isn't started
> on the destination host. So I'm left with a machine that had an
> improper shutdown...
> 
> If a live migration isn't reliable, I'm thinking to migrate as such: -
> guest is still runing - copy or rsync the disk image to the
> destination - shut down the guest - rsync the disk image again (to
> minimise the off-line period) - dumpxml of guest and copy to
> destination - define and start the guest on the destination
> 
> With the methode of the live migration, the machine will be
> unresponsive for max 20s = 20000ms (or less if I chose to). The
> migration it self will take op to 5 hours but I guess I plan these
> nightly.
> 
> With the other migration the guest will be really off-line for the
> duration of the (second) rsync. In my case with disk images from 50 to
> 150Gb, the rsync wil take up at least 30 minutes and every connection
> will be closed...
> 
> Does any body has good experiences with live migrations (without
> shared storage)? Any tips?
> 
> Any thoughts on the second method of migrating?

While no immediate answer on why your guest on destination host doesn't
start, but I've previously successfully tested wih qemu+tcp URI and
these three variants, without shared storage:

(1) Native migration, client to two libvirtd servers

    $ virsh migrate --verbose --copy-storage-all \
        --live cvm1 qemu+tcp://kashyapc@desthost/system

(2) Native migration, peer2peer between two libvirtd servers:

    $ virsh migrate --verbose --copy-storage-all \ 
         --p2p --live cvm1 qemu+tcp://kashyapc@desthost/system

(3) Tunnelled migration, peer2peer between two libvirtd servers:

    $ virsh migrate --verbose  --copy-storage-all \
        --p2p --tunnelled --live cvm1 qemu+tcp://kashyapc@desthost/system


Related notes here:

    https://bugzilla.redhat.com/show_bug.cgi?id=1202453#c19

-- 
/kashyap