Once you have set up a glusterfs volume, you might want to expand the volume to add storage. This is an astoundingly easy task.
The first thing that you’ll want to do is to add in bricks. Bricks are similar to physical volumes a la LVM. The thing to bear in mind is that depending on what type of cluster you have (replicated / striped), you will need to add a certain number of blocks at a time.
Once you have a initialised the nodes, to add in a set of bricks, you need the following command which adds two more bricks to a cluster which keeps two replicas.
$ gluster volume add-brick testvol cserver3:/gdata cserver4:/gdata
Once you have done this, you will need to rebalance the cluster, which involves redistributing the files across all the bricks. There are two steps to this process, the “fixing” of the layout changes and the rebalancing of the data itself. You can perform both tasks together.