How to check for split-brain in GlusterFS

A GlusterFS replicate volume can hide split-brain until an application reads a conflicted path or a heal attempt stalls. Checking the split-brain list before choosing a winner tells the operator which paths or GFIDs need manual resolution and which bricks reported them.

GlusterFS reports the split-brain subset through gluster volume heal <VOLNAME> info split-brain. The broader heal info output can also tag entries with Is in split-brain, but the split-brain-only form keeps the check focused on conflicts that automatic self-heal cannot safely choose.

Run the check from a node in the trusted pool against the volume that owns the replica set. A clean result shows zero split-brain entries for each brick; a nonzero result should be recorded and resolved only after the correct replica copy is identified.

1. List available volumes to confirm the target volume name.

   $ sudo gluster volume list
   volume1

2. Confirm the target volume is a started replicate volume.

   $ sudo gluster volume info volume1
   Volume Name: volume1
   Type: Replicate
   Status: Started
   Number of Bricks: 1 x 2 = 2
   Transport-type: tcp
   Bricks:
   Brick1: node1:/srv/gluster/brick1
   Brick2: node2:/srv/gluster/brick2
   Options Reconfigured:
   cluster.self-heal-daemon: enable

   Split-brain checks apply to replicate, distributed-replicate, and arbiter layouts where Automatic File Replication (AFR) tracks replica state.

3. List split-brain entries for the target volume.

   $ sudo gluster volume heal volume1 info split-brain
   Brick node1:/srv/gluster/brick1
   /dir/file1
   /dir/file4
   Number of entries in split-brain: 2
   
   Brick node2:/srv/gluster/brick2
   /dir/file1
   /dir/file4
   Number of entries in split-brain: 2

   No split-brain entries are indicated by Number of entries in split-brain: 0 on each brick.

4. Record the listed paths, GFID strings, parent directories, and reporting bricks before attempting resolution.

   GFID split-brain can appear as a gfid: entry or as the parent directory of the affected file. Resolution selects one replica copy as authoritative and can permanently overwrite the other copies.