If there’s one things that disks do well, it’s fill up and run out of room. My Openfiler iSCSI volumes always seem to be filling up as the virtual machines that live in them grow or I make snapshots.
If there is free room in the volume group that a volume is housed in, it’s very easy to make a volume larger with Openfiler. See my updated Openfiler wiki pages for some notes on this.