[Gluster-users] chances of split brain with a distributed replicated volume where replica is 3

[Joseph Lorenzini]

All:

I read this in the gluster docs. Note I am not using arbiter -- I am
setting up volumes with full 3 replicas. In this case, is this split brain
scenario theoretical or has this actually occurred? If so, what are the
chances that this could happen? In other words, aside from doing regular
snapshots, is this type of split brain scenario something I should be
planning in an unlikely disaster recovery scenario *or *part of daily
maintenance? Since the docs say its a corner case, I am inferring that this
is pretty unlikely.

"There is a corner case even with replica 3 volumes where the file can end
up in a split-brain. AFR usually takes range locks for the {offset, length}
of the write. If 3 writes happen on the same file at non-overlapping
{offset, length} and each write fails on (only) one different brick, then
we have AFR xattrs of the file blaming each other."

https://gluster.readthedocs.io/en/latest/Administrator%20Guide/arbiter-volumes-and-quorum/#replica-2-and-replica-3-volumes

Thanks,
Joe
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