[cinder] ceph multiattach details?
sean.mcginnis at gmx.com
Tue May 28 13:33:23 UTC 2019
On Tue, May 28, 2019 at 08:57:17AM -0400, Erik McCormick wrote:
> On Tue, May 28, 2019, 8:29 AM Bernd Bausch <berndbausch at gmail.com> wrote:
> > Thanks for clarifying this Erik. Let me point out then that the release
> > notes  are worded rather unequivocally, and what you are saying
> > contradicts them:
> > RBD driver has added multiattach support. It should be noted that
> > replication and multiattach are mutually exclusive, so a single RBD volume
> > can only be configured to support one of these features at a time.
> > Additionally, RBD image features are not preserved which prevents a volume
> > being retyped from multiattach to another type. This limitation is
> > temporary and will be addressed soon.
> > Bernd.
> I haven't even looked at Stein yet so I could be wrong, but I thin this is
> referring to replication like RBD mirroring. There's still an issue in
> Ceph, as far as I know, where ceph's object replication would have a
> problem with multi-attach. I haven't come across any Ceph release note to
> say this has been addressed.
> Hopefully someone from the Cinder team can straighten us out.
Multiattach support has indeed been enabled for RBD as of the Stein release.
Though there are the known caveats that you point out.
I thought there was a pending patch to add some details on this to to the RBD
driver configuration reference, but I am not finding anything at the moment.
I don't have all the details on that myself, but hopefully one of the RBD
driver maintainers can chime in here with better details.
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