What are you using FRA for? If you use it for backup, etc, and the way it was meant to be, than it needs to be much larger than your DATA volume. I think it should be at least 2 twice as large, better 3 times at least. So if your RAID setup using disks 3 - 6 does not provide enough disk space to accommodate the DATA and FRA disk groups you cannot proceed. Also if there is a performance difference between DATA and FRA one or the other can slow down the whole system. FRA and DATA should, but not necessarily, be on different physical storage for disaster recovery.