On Sat, 06 Mar 2010 18:17:44 -0500
"Guy Watkins" [off-list ref] wrote:

} 
} At a minimum I would build a 3-disk raid 6.  raid 6 does a lot of i/o
} which may be a problem.

If he only needs 3 drives I would recommend RAID1.  Can still loose 2 drives
and you don't have the RAID6 I/O overhead.

and as md/raid6 requires at least 4 drives, RAID1 is not just the best
solution to survive two failures on a 3-device array, it is the only solution.

NeilBrown