> >
> > Hi all,
> >
> > we are observing a problem on a libvirt virtualisation cluster that
> might come from ceph rbd clients. Something went wrong during execution
> of a live-migration operation and as a result we have two instances of
> the same VM running on 2 different hosts, the source- and the
> destination host. What we observe now is the the exclusive lock of the
> RBD disk image moves between these two clients periodically (every few
> minutes the owner flips).
>
> Hi Frank,
>
> If you are talking about RBD exclusive lock feature ("exclusive-lock"
> under "features" in "rbd info" output) then this is expected. This
> feature provides automatic cooperative lock transitions between clients
> to ensure that only a single client is writing to the image at any
> given time. It's there to protect internal per-image data structures
> such as the object map, the journal or the client-side PWL (persistent
> write log) cache from concurrent modifications in case the image is
> opened by two or more clients. The name is confusing but it's NOT
> about preventing other clients from opening and writing to the image.
> Rather it's about serializing those writes.
>
I can remember asking this also quite some time ago. Maybe this is helpful
https://www.wogri.at/scripts/ceph-libvirt-locking/
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