On Wed, Jun 18, 2025 at 7:29 PM Julien Laurenceau
<[email protected]> wrote:
>
> Hi,
>
> I have 2 running ceph squid clusters (19.2.2).
> On each cluster there is an rbd pool named k8s-1 that I want to mirror
> using the snapshot based mode.
>
> if I configure both clusters in two way mirroring using the mode=image
> everything works fine.
> ```
> rbd mirror pool enable ${mypool} image
> rbd mirror image enable ${mypool}/${myimage} snapshot
> ```
> When I take a snapshot of myimage it gets mirrored.
>
> if I configure both clusters in two way mirroring using the mode=pool
> nothings happen.
> The snapshot are never mirrored in the second cluster.
>
> Reading the documentation https://docs.ceph.com/en/squid/rbd/rbd-mirroring/,
> I think that the problem is that the default mode for this command is
> "journal":
>
> rbd mirror image enable {pool-name}/{image-name} {mode}
>
> But, when enabling mirror on the pool there is no way to define
> mode=journal/snapshot:
>
> rbd mirror pool enable [--site-name {local-site-name}] {pool-name} {mode}
>
> with mode=pool (default) or image.
>
> Then I think when I do :
> rbd mirror pool enable ${mypool} image
>
> I think it implicitly do :
> rbd mirror pool enable ${mypool} image journal # THIS COMMAND DOES NOT
> WORK.
>
> But I would need to have:
> rbd mirror pool enable ${mypool} image snapshot # THIS COMMAND DOES NOT
> WORK.
>
>
> In addition, when I am configured on mirror mode = pool, if I try to
> disable mirroring on an image I get the following error :
> rbd mirror image disable ${mypool}/${myimage}
> 2025-06-18T15:37:42.177+0000 7f24ec53ce00 -1 librbd::api::Mirror:
> image_disable: cannot disable mirroring in the current pool mirroring mode
>
> Also error when I am configured on mirror mode = pool, if I try to enable
> snapshot mirroring on an image :
> rbd mirror image enable ${mypool}/${myimage} snapshot
> 2025-06-18T15:39:44.507+0000 7f533df1fe00 -1 librbd::api::Mirror:
> image_enable: cannot enable mirroring: pool is not in image mirror mode
>
> Could someone please confirm, that this is not supported ?
Hi Julien,
Yes, snapshot-based mirroring is possible only in "image" mode. The
"pool" mode is limited to journal-based mirroring. It's stated in the
documentation, but perhaps not explicitly enough:
You can also mirror all images within a given pool or namespace when
using journal-based mirroring.
>
> What is the best workaround ? Cron cephadm shell script to enable mirror on
> all images ?
>
> PS : I do not want to use the journal based mode since the ceph-csi mounter
> nbd is not prod-ready.
If you are using Ceph CSI, it would be much better to drive mirroring
through Ceph CSI -- see VolumeReplication and related resources.
Thanks,
Ilya
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