Yeah there was a thread on the FCP forum about this card a few weeks ago. I was talking to the guys at Atto about it and they were filling me on some of the differences between the Apple card and Atto's R-380 SAS/SATA cards that we just purchased here.
Apple offers a x4 PCIe bus which can limit total bandwidth to 1GB of performance. ATTO ExpressSAS RAID has a x8 PCIe bus delivering 2GB of bandwidth.
Apple is limited to one internal x4 connector that connects to either SATA or SAS drives. ATTO ExpressSAS RAID can direct connect up to 8 SAS/SATA drives or more through SAS Expanders.
In RAID 5, the Atto cards outperform in both Read and Write speeds over the Apple cards, up to 27% faster.
Of course the big thing right now is that the Apple card is only offered on a configure to order basis on a new machine while you can simply pick up an R380 for any PCIe machine.
The one thing I don't get about Apple is why their mass storage products are so expensive when just about any other product on the market outperforms them. A fully populated, 14 drive X-RAID gets something like 176MB/s in RAID 5. My 8 drive, 8TB MaxxDigital SATA array topped out at 516MB/s in RAID 5. At a price I believe is less than half the price of the fully populated X-RAID.
The Sonnett 8TB RAID we tested topped out around 460MB/s. The Dulce 8TB RAID we tested topped out around 275MB/s. So while Apple makes killer computers, they just seem to be outperformed by just about everyone else out there when it comes to mass storage.
It's nice to see Apple offer this RAID option, but it sure would be nice to see more performance from a $999 card.