The ATA arrays may be configured the same as FC arrays (number of drives in the RAID group, stripe size and parity protection) or may be completely different, but that doesn't matter when the data is accessed from the storage controller by a server.
Certainly you could consider the way the storage controller accesses the data a hardware and software change, but that is necessary because the physical interface is different and the command set used (SCSI vs. ATA) is different. That is all hidden from the outside world and self-contained in the storage system.
The drives themselves cannot be intermixed within a RAID group in products today.
This was first published in April 2005