It seems fakeraid is detected on sdc and sdd, ut not on sda and sdb. All 4 drives are part of the same software RAID-5 provided by the NAS-XSR. The only real difference I see is that both the sdc and sdd are RAID Edition verions of Western Digital 250GB SATA drives..... The other two are regular 250GB drives. Could this be the cause?
This should not mater. I have set up many non RAID Edition drives mixed with RAID Edition drives and still not have a problem. Now I do recommend using the RAID Edition drives depending on manufacture (I like the Hitachi drives) and keeping continuity of the drive specs.