[Gluster-users] When to use Arbiter volumes and quorum options?

[Alexandr Porunov]

Hello Ravi,

Thank you for the explanation! Now it is clear

Best regards,
Alexandr

On Sat, Nov 26, 2016 at 3:07 PM, Ravishankar N <ravishankar at redhat.com>
wrote:

> On 11/26/2016 04:54 PM, Alexandr Porunov wrote:
>
> Hello,
>
> 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?
>
> I tried to achive a split-brain in a replicated voulume 3 but couldn't.
> Does GlusterFS manage split-brain situations automaticaly?
>
> I tried following:
> node1, node2, node3 is the nodes with a replicated volume.
> 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.
>
> 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.
>
> 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?
>
>
> 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.
>
> You can find more information @ http://gluster.readthedocs.io/
> en/latest/Administrator%20Guide/arbiter-volumes-and-quorum/ and
> http://events.linuxfoundation.org/sites/events/files/slides/
> glusterfs-arbiter-VAULT-2016.pdf
>
> Regards,
> Ravi
>
> Sincerely,
> Alexandr
>
>
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>
>
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