Reminder -- RAID 5 is not your friend

[Derek Atkins]

Richard Pieri <richard.pieri-Re5JQEeQqe8AvxtiuMwx3w at public.gmane.org> writes:

> You've thrown money at the problem without improving reliability.
> RAID 10 is not more reliable than RAID 5.  RAID 10 requires a minimum
> of 4 disk.  A1 is mirrored to B1 and A2 is mirrored to B2.  *1 and *2
> are then striped together.  What happens when you lose A1 and B1?
> Answer: you lose your data.

The difference is that with RAID10 you have to lose two SPECIFIC disks
in order to lose data, whereas with RAID5 you only need to lose ANY two
disks.  So, in RAID5 you could lose A1 and A2 and you're toast, whereas
if you lose A1 and A2 in a RAID10 setup you still have all your data.

So I think that RAID10 is *slightly* less risky than RAID5.

In fact, if you lose the *right* set of disks you can lose 50% of your
disks in RAID10 and still not lose your data.  :-D

-derek
-- 
       Derek Atkins, SB '93 MIT EE, SM '95 MIT Media Laboratory
       Member, MIT Student Information Processing Board  (SIPB)
       URL: http://web.mit.edu/warlord/    PP-ASEL-IA     N1NWH
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