Convert GlusterFS Volume from Distributed-Replicated to Replicated

You have an existing gluster volume "gv0" backed by 4 bricks from each server.
There are a total of 4 gluster servers.

1. Remove 2 bricks from. Number of bricks to be remove must be multiple of the
   total number of bricks.

   gluster volume remove-brick myvolume node{3..4}:/bricks/gv0/brick1 start

   The "start" at the end tells gluster to move existing data from the bricks
   being removed to the remaining bricks.

2. Check the status of data migration. Make sure it is completed before
   proceeding to next step.

   gluster volume remove-brick myvolume node{3..4}:/bricks/gv0/brick1 status

3. Re-add the 2 bricks to form a 4-way replicated volume.

   gluster volume add-brick myvolume replica 4 node{3..4}:/bricks/gv0/brick1

4. You might notice that the re-added bricks' size are smaller than what is
   expected. Some files seems still not present on them but any access to those
   missing file will make them appear on the bricks. A simple `ls` will make
   the files reappear.