We're running a 500GB RAID 1 on an Adaptec 2420SA - 2x500GB Hitachi Drives. It suddenly crashed and required a rebuild -- was not even booting. It's only at 66% after about a week. Very frustrated. This is the second box with the same card and drives that has had issues with the RAID/drives. Another box had this happen twice. Both machines are Linux boxes. CentOS and Fedora.
I dunno if it's the firmware -- which currently needs an update (any help doing this over PXE would be great- I have used UDA to do PXE boots in the past).
Anyway, would love to hear about experiences with this card and firmware. I thinking of going google and just using cheap boxes no raid and have server redundancy instead.