Yeah the intel stuff and/or on board raid is FCKing crap.
I have a Raid 10 defined on Asus P577D and always (~14days) a different drive gets degraded.
Sometimes the whole array gets corrupted.
Well, I guess I found my issue. The Seagate Barracuda 7200.10 drives must be for CRAP. I got a set of 7200.12 drives put em in, built the mirror, restored from backup and problem gone. Can pull a drive and it rebuilds to spare no problem.