Mac Pro RAID

I have a 2008 Mac Pro 3.1 with 4 300GB SAS drives. The boot volume is a 480GB SSD, approaching 290GB used. Before I installed the SSD, SAS 1 was my boot drive, SAS 2 was a backup. Since I installed the SSD, SAS 1 and SAS 2 have been alternating backups. Now the SSD main drive is too full for a 300GB backup drive, so I want SAS 1 and 2, and SAS 3 and 4, striped into two RAID drives, preferably using the RAID utility. Worked fine with drives 3 and 4, but RAID utility wouldn’t recognize 1 and 2 as drives eligible for RAID (the “Create RAID Set” icon wouldn’t highlight, as it had for drives 3 and 4). I was able to stripe 1 and 2 into a RAID array using the Disk Utility, but the result is a little weird. RAID Utility recognizes the following VOLUMES, RAID SETS, and DRIVES:

VOLUMES: Boot OSX (drive 1), Boot OSX (drive 2), and RAID Set2 (drives 3 and 4)

RAID SETS: R0-1 (drive 1, 300GB), R0-2 (drive 2, 300GB), and RS1 (drives 3 and 4, 600GB)

DRIVES: Bay 1 (300GB), Bay 2 (300GB), Bay 3 (300GB), Bay 4 (300GB)

That is, RAID Utility seems to see Bay 1 and Bay 2 as two individual RAID drives, and Bays 3 and 4 as a single unified RAID drive (as I'd hoped).

Disk Utility sees drives 3 and 4 only as a single RAID drive, but sees drives 1 and 2 individually (labelling them “slices” AND ALSO sees them as a combined RAID set of 600GB.

Finder simply sees 2 RAID devices of 600GB each (although the icons are different).

Anyone able to clarify what’s going on? Can I just ignore RAID Utility and the other aberrant signs and use these two RAID arrays as alternating backups as I planned?