I ran some benchmarks; this time I ran them with a larger data set, as the 512mb cache on the RAID card throws off benchmarks. We need to test the drive arrays, not the RAID card cache.
four drive RAID5 146gb 15k SAS
two drive RAID1 1tb WD Entperise SATA
two drive RAID1 1tb WD Red NAS SATA
I am really surprised that WD Red NAS drives out performed the WD Enterprise (WD1003FBYZ) drives. Both are 64gb cache, the Reds are 5400~7200 rpm (Intelipower) and the Ent. are 7200rpm.