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<div class="moz-cite-prefix">On 11/26/2016 04:54 PM, Alexandr
Porunov wrote:<br>
</div>
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<div>Hello,</div>
<div><br>
</div>
<div>I am using GlusterFS 3.8.5. I wonder to know when to use
Arbiter volumes and quorum options in GlusterFS and what
difference between them?</div>
<div><br>
</div>
<div>I tried to achive a split-brain in a replicated voulume 3
but couldn't. Does GlusterFS manage split-brain situations
automaticaly?</div>
<div><br>
</div>
<div>I tried following:</div>
<div>node1, node2, node3 is the nodes with a replicated volume.</div>
<div>I have created a network crash between node1 and node3 but
node1 and node3 still can speak with node2. When I write a
file to node1 it automatically creates on node2 and node3.
When I write a file to node3 it automaticaly creates on node2
and node1.</div>
<div><br>
</div>
<div>I tried to crash node1 then write to node3 and then crash a
node3 and recover node1. Still it works just fine. I tried to
crash two nodes and then write to the healthy node and it
doesn't work. After I have run one more node it started work.</div>
<div><br>
</div>
<div>Is it possible to achive a split-brain in a GlusterFS
cluster 3.8.5? If yes then how and what options we have to set
to prevent split-brain? If no then why do we need an arbiter
and quorum options?</div>
<div><br>
</div>
</div>
</blockquote>
<br>
Split-brains are possible in replica-2 volumes. They don't occur in
replica-3 volumes or arbiter-volumes. Client-quorum is enabled and
set to 'auto' when you create replica-3 or arbiter vols. You're not
supposed to change it. Arbiter vols can be used if you want to avoid
split-brains but don't want to invest in a 3rd data brick for
replica-3. Of course, the availability of arbiter is less compared
to replica-3 because we don't store the actual file content in the
3rd (arbiter) brick.<br>
<br>
You can find more information @
<a class="moz-txt-link-freetext" href="http://gluster.readthedocs.io/en/latest/Administrator%20Guide/arbiter-volumes-and-quorum/">http://gluster.readthedocs.io/en/latest/Administrator%20Guide/arbiter-volumes-and-quorum/</a>
and
<a class="moz-txt-link-freetext" href="http://events.linuxfoundation.org/sites/events/files/slides/glusterfs-arbiter-VAULT-2016.pdf">http://events.linuxfoundation.org/sites/events/files/slides/glusterfs-arbiter-VAULT-2016.pdf</a><br>
<br>
Regards,<br>
Ravi<br>
<br>
<blockquote
cite="mid:CAB-_WnF=XkW_F8nU6c+C+kAXZgYdGPz_zRDrDQA+VB_adFKTcw@mail.gmail.com"
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<div>Sincerely,</div>
<div>Alexandr</div>
</div>
<br>
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</blockquote>
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