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.

1. 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)

   Related: How to set up a trusted storage pool for GlusterFS

2. 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 disks and partitions in Linux
   Related: How to get disk and partition UUIDs in Linux

3. 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.

4. Start the new volume.

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

5. 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.

6. 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