We aren't sure whether to use software MDRaid or a MegaRAID card.
Never go with hardRaid. I have had a breakdown on a hardware RAID and as it was special and not off-the-shelf, I could not move the disk to another controller. I think it was a capacitor, maybe capasitor plaegue.
Only thing I had to do was to restore to the day before and the customer lost one days work.