Desktop / Consumer RAID Environments - WD Caviar Green Hard Drives are tested and recommended for use in consumer-type RAID applications (RAID-0 /RAID-1) this is from WDs website.
I am running 2 WD20EARS in a raid 0 and all is well atm.  Been running 2 months..  One prob is supposed to be in a raid one if one drive fails and can't work thru a rebuild?  Not running raid 1, havent tried JBOD.. so who knows..  I do know the 321 doesnt use NFTS format and I am not that familar with it's formats..