Bug#539059: Suspending SATA hard disks degrades software RAID 1
I'm also seeing this problem on 2.6.31 with sw raid5 and sata drives. Sending drives in the raid to sleep via hdparm -Y causes all drives in the raid to fail simultaneously, requiring a stop and forced reassembly of the raid to bring it back online.
So I'd be interested aswell, if an upstream ticket exists for this problem.
Here is a log of what happened: http://pastebin.com/Vb3LMc38
Note this is on an NVidia ION/Atom system using the ION sata ports.