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

Ravishankar N ravishankar at redhat.com
Thu Feb 9 13:52:21 UTC 2017

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,
> Joe
> _______________________________________________
> Gluster-users mailing list
> Gluster-users at gluster.org
> http://lists.gluster.org/mailman/listinfo/gluster-users

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.gluster.org/pipermail/gluster-users/attachments/20170209/cee5ad3a/attachment.html>

More information about the Gluster-users mailing list