[Gluster-users] HA replica

[Mike Stump]

On Feb 13, 2016, at 6:21 PM, Ravishankar N <ravishankar at redhat.com> wrote:
> Like Bishoy said in another thread, quorum does not really make sense in 2-replica  because there is no notion of majority. 

Ah, could you update the doc to note that a quorum isn’t formed from all the members of the cluster, but rather from the replicas and arbiters involved in the specific operation?  In a 10x3 cluster, it would be formed from just 3 nodes, not 30.

I expected that in a 10 (5x2) server setup, 6 means majority.  Any island of 5 or less, would not be a majority.  Any island of 6 or more, would form a majority.  The doc isn’t clear on the point that in a 5x2 setup, the software won’t take a majority of all the cluster members.  I had assumed that all the cluster members would help form a quorum for the entire cluster.

Additionally, can you say that a replica 2 doesn’t help build an HA cluster.  One must have a replica 3, or an arbiter volume.  This let’s a person who specifically wants HA to avoid the mistake of replica 2.

Thanks.