Have you also created your partitions with a reasonably new fdisk (or
equivalent) with -c -u as options?
Your partitions should be starting somewhere at 2048 i guess (let the
sw figure that out). The fast degradation of the one disk might
indicate bad partitioning? (maybe recheck with a grml.iso or something
alike http://www.grml.org/ )
Also, ... did you know that any unused space in the disk is being used
as bad block 'replacement'? so just leave out 1-2 GB space at the end
of your disk to make use of this 'feature'
otherwise, mdadm supports raid1 with more than 2 drives. I havent seen
this configuration much but it makes absolute sense on drives where
you expect failure. (i am not speaking spare, but really raid1 with >
2 drives).
I like this setup, with ssd drives it might be the solution to decay.
regs,
klaus
