Alexandr Porunov
2016-Nov-26 11:24 UTC
[Gluster-users] When to use Arbiter volumes and quorum options?
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? Sincerely, Alexandr -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://www.gluster.org/pipermail/gluster-users/attachments/20161126/83675120/attachment.html>
Ravishankar N
2016-Nov-26 13:07 UTC
[Gluster-users] When to use Arbiter volumes and quorum options?
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>