26.04.2016 13:00, Kashyap Chamarthy пишет:
On Tue, Apr 26, 2016 at 06:26:59AM +0300, Maxim Nestratov wrote:
Hi,
As far as I understand, currently there is no way to live migrate qemu
VMs that have internal snapshots, because live migration works via
qemu drive mirroring, which in turns mirrors only shallow block layer,
effectively losing existing embedded snapshots. The problem could be
fixed if we created an external delta for all disks with internal
snapshots, live migrate such VMs and then auto merge them back into
original images. That said, I would like to know very much your
opinion on the matter and would also like to know if this approach is
affordable. If so, I or one of my colleagues will send a pathset to
fix this, otherwise what solution for this problem you will recommend?
There seems to be an old discussion here[1] on this topic:
"You are not the first to request this - libvirt would
also like the ability to have read-only access into the contents of an
internal snapshot while the rest of qemu continues to write into the
image." (Eric Blake)
When I asked if this was possible with today's QEMU, Kevin Wolf (QEMU
block layer maintainer) on #qemu IRC said:
"No, this requires some non-trivial code design changes and was
never considered important enough. This would also require writes
to those snapshots on the destination, by the way (which wouldn't be
impossible if the infrastructure for having multiple active
snapshots at the same time were there)"
[1]
http://lists.nongnu.org/archive/html/qemu-devel/2012-11/msg00402.html --
live migration which includes previos snapshot
Hmm. Interesting. But what I'm talking about doesn't involve qemu much.
We create
an external temporarily delta for images with internal snapshots on
libvirt side,
then merge it on libvirt side thus, qemu shouldn't be affected at all as
far as I
understand.
Copying my colleagues to the thread.
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