[Gluster-users] HA replica
b.s.mikhael at gmail.com
Fri Feb 12 20:02:27 UTC 2016
I don’t understand why do u want to set quorum with only two servers. It doesn’t make sense at all!
simply create a distributed replicated volume with no quorum on your two nodes cluster, when one node goes down, the volume will still be RW without any problems.
How come you do want to set quorum on only two nodes cluster?!
To set quorum add at least a third node, so when you have a failed node, the other two will still serve the volume as RW.
the definition of quorum is as follows:
The quorum configuration in a failover cluster determines the number of failures that the cluster can sustain. If an additional failure occurs, the cluster must stop running. The relevant failures in this context are failures of nodes or, in some cases, of a disk witness (which contains a copy of the cluster configuration) or file share witness. It is essential that the cluster stop running if too many failures occur or if there is a problem with communication between the cluster nodes.
hopefully this made you better understand what’s quorum, there is no difference between a network partition and a quorum in a cluster of two nodes. that’s why I said what you are trying to do doesn’t make sense.
> On Feb 12, 2016, at 11:32 AM, Mike Stump <mikestump at comcast.net> wrote:
> On Feb 12, 2016, at 8:34 AM, Ravishankar N <ravishankar at redhat.com> wrote:
>> Consistency, availability, tolerance to network partitions. You get to pick any two.
> I wanted the first two. I did not get them. By default, we get split brain. This means no consistency. To cure that, we choose quorums. But when the first of a replica 2 pair goes away, you then loose write access. Without write, we loose availability. So, if you think it is possible, let me know how to reconfigure my array and I will tell you if it worked. If you could update the docs to explain how you get the first two, that would be nice. If you could update the docs to state that the array goes into a partial read-only state if a replica pair goes away, that would be nice.
> I’m fine with running in a degraded state when a server goes away. When it comes back, I want it to suck down all the new changes from the authoritative replica pair known to the quorum and then once it has all the data, then it can be marked as not-degraded and resume normal operation.
> I want each node to notice a down server, and when it is part of a 51% partition, I want the remaining replica members of that server to become degraded replica N-1 set. When the server comes back up, and want it to repair back into a replica N state.
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