How to create a GlusterFS arbiter volume

An arbiter volume adds a third GlusterFS brick that stores metadata only, reducing split-brain risk without paying the full 3× storage cost of a traditional three-way replica.

Arbiter volumes are replicated volumes in an (2 + 1) layout: two bricks store file data, and the third brick stores directory entries, file names, and metadata to participate in quorum decisions and break ties during healing.

The arbiter brick should run on a separate node to preserve fault-tolerance characteristics and should use reliable storage and networking. An arbiter brick is not a third copy of data, so availability remains “tolerate one brick down”; losing the arbiter plus one data brick can block I/O due to quorum rules.

Steps to create a GlusterFS arbiter volume:

Check peer connectivity in the trusted storage pool.

$ sudo gluster peer status
Number of Peers: 2

Hostname: node2
Uuid: 0f3e0b7c-2e59-4c73-9c1c-3e65b6c1e8c9
State: Peer in Cluster (Connected)

Hostname: node3
Uuid: 8b7e3e2a-1a6e-4f2b-b4a6-2a0b9a4f7a6d
State: Peer in Cluster (Connected)

Create an empty brick directory on each node intended to host a brick.
```
$ sudo mkdir -p /srv/gluster/brick1
```
Use a dedicated filesystem for production bricks to avoid filling the system volume.

Related: How to mount a disk or partition in Linux
Related: How to get a disk or partition UUID in Linux

Create the arbiter volume with two data bricks and one arbiter brick.

$ sudo gluster volume create volume1 replica 2 arbiter 1 transport tcp node1:/srv/gluster/brick1 node2:/srv/gluster/brick1 node3:/srv/gluster/brick1
volume create: volume1: success: please start the volume to access data

The last brick in each (2 + 1) set becomes the arbiter brick.

Some GlusterFS versions also accept replica 3 arbiter 1 for the same (2 + 1) layout.

Start the new volume.

$ sudo gluster volume start volume1
volume start: volume1: success

Verify the volume reports an arbiter layout and brick list.

$ sudo gluster volume info volume1
Volume Name: volume1
Type: Replicate
Status: Started
Number of Bricks: 1 x (2 + 1) = 3
Bricks:
Brick1: node1:/srv/gluster/brick1
Brick2: node2:/srv/gluster/brick1
Brick3: node3:/srv/gluster/brick1 (arbiter)

Some versions omit the (arbiter) suffix and only list the three bricks.

Confirm the bricks and self-heal daemons are online.

$ sudo gluster volume status volume1
Status of volume: volume1
Gluster process                             TCP Port  RDMA Port  Online  Pid
------------------------------------------------------------------------------
Brick node1:/srv/gluster/brick1             49152     0          Y       1873
Brick node2:/srv/gluster/brick1             49152     0          Y       1934
Brick node3:/srv/gluster/brick1             49152     0          Y       2011
Self-heal Daemon on node1                   N/A       N/A        Y       2098
Self-heal Daemon on node2                   N/A       N/A        Y       2147
Self-heal Daemon on node3                   N/A       N/A        Y       2210