NOTE: If more than 2 drives fail, you may have to do an interactive startup to stop the auto alarm posting of the "Iscsi target" service.  The alarm will hamper entering of the command.

If you are trying to use OpenFiler 2.3 as a storage repository for Citrix XenServer and a drive fails or the raid is broken, OpenFiler does not automatically repair the raid if a new drive is added or the issue with the previous drive is resolved and it is reinstalled. You have to re-attach the volume(s) manually to the raid device in Openfiler.

To see the members of the raid device, login to the OpenFiler GIU via your web browser --> volumes --> software Raid, then click on view members.  Here you will see the Raid configurations and which drives/volumes have been detached. Alternative methods would be to view the OpenFiler error email or execute the following command at the CLI (command line interface):

cat /proc/mdstat

The above command prints on the current system raid settings.

To reSync the array device, you must use of the “mdadm” command from the CLI:

mdadm /dev/md0 --add /dev/sdb1

The above example adds the partition/volume sdb1 to the raid device md0.

The status of the rebuilding/syncing of the raid can then be seen from the web interface of OpenFiler:  Volumes --> Software Raid.

Credit to: https://forums.openfiler.com/viewtopic.php?id=1768