I did the same with openfiler, has worked well for about 4+ years. It has 4x400GB in RAID5 which gives 1.2TB of storage. I've been planning an upgrade to 4x2TB

I did the same with openfiler, has worked well for about 4+ years. It has 4x400GB in RAID5 which gives 1.2TB of storage. I've been planning an upgrade to 4x2TB for a 6TB RAID, but I haven't had the time or the $ for the upgrade. I used some of the storage space as a time machine destination, but Apple has issues with Time Machine over SMB, and it got to the point where it was too slow, so I bought an USB disk and just back-up to that.