I have a couple of the old Intel SS4000E 4-way RAID boxes. They supported RAID 0/1/5/5+spare & JBOD. Their main use is for scratch storage for a small group of workers and the redundancy gain from either mirroring or parity. I think they have their place, though I paid a lot less than that for mine. Shame in a way that Intel don't make them anymore.

Usually these things use their system processor to do the raid, that said a well optimized box can be just as fast as a good hardware raid solution just by dint of throwing enough FSB and ram at the problem.

Don't expect to see a $400 RAID adapter in a $800 NAS is all, particularly since said raid adapters are horrible overkill for the (likely load-shared) giga-lan this thing will jack into.

Via a datasheet
"Enhance data integrity and/or performance with RAID 0/1/5/10 & JBOD configuration options."
also
"The BlackArmor NAS 420 storage server contains four drive bays, two drives are included. Three drives are need for RAID 5 and four drives are need for RAID 10."

But that's about the best I can find on their site.

Do you mean the box contains a built-in RAID controller or merely that once I have 4 USB disks plugged into a machine I might choose to make a software RAID array?

If the box has a built-in RAID controller, then what is it, what company makes it?