The other day I was testing a 24 drive RAID with Seagate Barracuda ES 750Gig drives on a Areca 1680 SAS card. Rsyncing terabytes of data from other systems was perfect. So an order was put in to the vendor for the same RAID units. The vendor said that the Barracuda ES drives where end-of-life. They where being replaced with Barracuda ES.2 750's. I figured how much could a .2 really make a difference. I'm here to tell you A LOT!
When the units came in every piece of hardware was the same except for the newer model of the same class hard drives we have. The RAID's initialized fine. Then we started to rsync data to them. After a ~20 hours of syncing the drives started giving the error "Time Out Error" in the RAID card's logs. The card would be come unresponsive after a while. Sometimes a drive or two would drop out completely and the RAID would become degraded.
After searching and searching on this problem I came across this entry in the Areca FAQ. I also saw this in the 3ware knowledge base. Both state problems with the Seagate Barracuda ES.2 drives and a certain firmware. There was a new firmware out to fix the problem. The drives I had did not have the newer firmware so after flashing the drives with the newer firmware everything was fixed. There is a good thread about this on Seagate's site here. From the thread Seagate support does not sound very helpful with this issue.
If your using Seagate Barracuda ES.2 family drives (NS) models ST31000340NS, ST3750330NS, ST3500320NS, or ST3250310NS with firmware SN04 or 05 with a raid card and you are experiencing problems you might need to update to the AN05 firmware.
This problem really speaks to only taking the exact system you tested and never accepting any minor changes without re-testing. That was my bad.