Hi Jason,
... also forgot to mention "rbd export --export-format 2" / "rbd
import --export-format 2" that will also deeply export/import all
snapshots associated with an image and that feature is available in
the Luminous release.
thanks for that information, this could be very valuable for us. I'll
have to test that intesively, but not before next week.
But a first quick test brought up a couple of issues which I'll have
to re-check before bringing them up here.
One issue is worth mentioning, though: After I exported (rbd export
--export-format ...) a glance image and imported it back to a
different pool (rbd import --export-format ...) its snapshot was
copied, but not protected. This prevented nova from cloning the base
image and leaving that instance in error state. Protecting the
snapshot manually and launch another instance enabled nova to clone
the image successfully.
Could this be worth a bug report or is it rather something I did wrong
or missed?
I wish you all a nice weekend!
Regards
Eugen
Zitat von Jason Dillaman <jdillama@xxxxxxxxxx>:
On Fri, Feb 16, 2018 at 8:08 AM, Jason Dillaman <jdillama@xxxxxxxxxx> wrote:
On Fri, Feb 16, 2018 at 5:36 AM, Jens-U. Mozdzen <jmozdzen@xxxxxx> wrote:
Dear list, hello Jason,
you may have seen my message on the Ceph mailing list about RDB pool
migration - it's a common subject that pools were created in a sub-optimum
fashion and i. e. pgnum is (not yet) reducible, so we're looking into means
to "clone" an RBD pool into a new pool within the same cluster (including
snapshots).
We had looked into creating a tool for this job, but soon noticed
that we're
duplicating basic functionality of rbd-mirror. So we tested the following,
which worked out nicely:
- create a test cluster (Ceph cluster plus an Openstack cluster
using an RBD
pool) and some Openstack instances
- create a second Ceph test cluster
- stop Openstack
- use rbd-mirror to clone the RBD pool from the first to the second Ceph
cluster (IOW aborting rbd-mirror once the initial coping was done)
- recreate the RDB pool on the first cluster
- use rbd-mirror to clone the mirrored pool back to the (newly
created) pool
on the first cluster
- start Openstack and work with the (recreated) pool on the first cluster
So using rbd-mirror, we could clone an RBD pool's content to a differently
structured pool on the same cluster - by using an intermediate cluster.
@Jason: Looking at the commit history for rbd-mirror, it seems you might be
able to shed some light on this: Do you see an easy way to modify
rbd-mirror
in such a fashion that instead of mirroring to a pool on a
different cluster
(having the same pool name as the original), mirroring would be to
a pool on
the *same* cluster, (obviously having a pool different name)?
From the "rbd cppool" perspective, a one-shot mode of operation would be
fully sufficient - but looking at the code, I have not even been able to
identify the spots where we might "cut away" the networking part, so that
rbd-mirror might do an intra-cluster job.
Are you able to judge how much work would need to be done, in order to
create a one-shot, intra-cluster version of rbd-mirror? Might it even be
something that could be a simple enhancement?
You might be interested in the deep-copy feature that will be included
in the Mimic release. By running "rbd deep-copy <src-image>
<dst-image>", it will fully copy the image, including snapshots and
parentage, to a new image. There is also work-in-progress for online
image migration [1] that will allow you to keep using the image while
it's being migrated to a new destination image. Both of these are
probably more suited to your needs than the heavy-weight RBD mirroring
process -- especially if you are only interested in the first step
since RBD mirroring now directly utilizes the deep-copy feature for
the initial image sync.
... also forgot to mention "rbd export --export-format 2" / "rbd
import --export-format 2" that will also deeply export/import all
snapshots associated with an image and that feature is available in
the Luminous release.
Thank you for any information and / or opinion you care to share!
With regards,
Jens
[1] https://github.com/ceph/ceph/pull/15831
--
Jason
--
Jason
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