How to configure GlusterFS client quorum

Client quorum in GlusterFS blocks writes when too few replica bricks are reachable, reducing split-brain and data divergence during partial outages or network partitions.

On replicated and distributed replicated volumes, the GlusterFS client sends each write to multiple bricks in the replica set. Client quorum enforces a minimum number of healthy bricks before I/O proceeds, causing operations to fail fast instead of writing to a minority and creating conflicting copies.

Client quorum improves consistency at the cost of availability, especially on replica 2 volumes where losing a single brick can stop writes when quorum requires both bricks. Quorum settings should match the replica count and maintenance expectations, and lowering quorum below a replica majority trades safety for availability and can reintroduce split-brain risk.

Steps to configure GlusterFS client quorum:

Identify the target GlusterFS volume name.
```
$ sudo gluster volume list
volume1
```
Set the client quorum policy for the volume using cluster.quorum-type.
```
$ sudo gluster volume set volume1 cluster.quorum-type auto
volume set: success
```
```
$ sudo gluster volume set volume1 cluster.quorum-type fixed
volume set: success
```
auto uses a replica majority; fixed requires cluster.quorum-count and is typically set to the same majority. Run only one of the two commands; the last applied value becomes effective for the volume.
Configure cluster.quorum-count when cluster.quorum-type is fixed.
```
$ sudo gluster volume set volume1 cluster.quorum-count 2
volume set: success
```
Set cluster.quorum-count to a replica majority (replica 3 → 2, replica 2 → 2); using a lower value allows writes on a minority and increases split-brain risk.

Verify the configured quorum policy for the volume.

$ sudo gluster volume get volume1 cluster.quorum-type
Option              Value
------              -----
cluster.quorum-type fixed

Verify cluster.quorum-count when using fixed quorum policy.

$ sudo gluster volume get volume1 cluster.quorum-count
Option               Value
------               -----
cluster.quorum-count 2