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

[Ravishankar N]

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


-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.gluster.org/pipermail/gluster-users/attachments/20161126/6e40a058/attachment.html>