Hi David, On Wed, Oct 20, 2021 at 6:23 AM David Cunningham <[email protected]> wrote:
> Hello, > > I've a few questions about conflict resolution in a net-split scenario: > > 1. What are the default values for cluster.server-quorum-type and > cluster.server-quorum-ratio? (at the moment "gluster volume info gvol0" > does not report either) > > $gluster volume get gvol0 cluster.server-quorum-type $gluster volume get all cluster.server-quorum-ratio > 2. If there are 3 mirrored nodes and cluster.server-quorum-ratio is 50, > and node1 and node2 are net-split from node3, then am I right in thinking > that the volume on node3 will automatically shut down and prevent access > thus preventing a conflict? > > Yes, the glusterd on node 3 will kill the brick processes on that node. > 3. If there are 2 mirrored nodes and a net-split happens and > cluster.server-quorum-ratio is 50 then: > a) If existing file A is changed on node1 and node2 then the file will > enter net-split state, right? > Yes, for 2 node setups, you must set the ratio to 51% to avoid this. I'm assuming that the 'changing' that you refer to is happening via fuse mounts on each of these nodes. > b) If existing file B is changed on node1 but not node2 then will the file > enter a net-split state? > No. > c) If new file C is written on node1 but not node2 then will the file > enter a net-split state? > > No. > 4. Is the outcome of conflict resolution at a file level the same whether > node3 is a full replica or just an arbiter? > > server quorum feature is not related to replication. It really is a glusterd thing and doesn't really help prevent split-brains, because split-brains are caused by failed I/Os from clients and the clients can be mounted even outside the storage pool. What you need to ensure is that cluster.quorum-type (which is 'client' quorum) is set to auto for replica 3 and arbiter. It already is by default. See https://docs.gluster.org/en/latest/Administrator-Guide/arbiter-volumes-and-quorum/#split-brains-in-replica-volumes for more info. -Ravi > Thank you very much for any advice, > > -- > David Cunningham, Voisonics Limited > http://voisonics.com/ > USA: +1 213 221 1092 > New Zealand: +64 (0)28 2558 3782 > ________ > > > > Community Meeting Calendar: > > Schedule - > Every 2nd and 4th Tuesday at 14:30 IST / 09:00 UTC > Bridge: https://meet.google.com/cpu-eiue-hvk > Gluster-users mailing list > [email protected] > https://lists.gluster.org/mailman/listinfo/gluster-users >
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