On 02/09/2017 06:39 PM, Joseph Lorenzini wrote:
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
I don't think you should be bothered about it too much as it is rare
for split-brains to happen in replica 3 (folks who have had experience
otherwise, please correct me:)). In the worst case, there are commands
to resolve split-brains as described in the link you shared above.
Thanks,
Ravi
Thanks,
Joe
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