Hard Disk IDs in Linux

Lonnie Olson lists at kittypee.com
Tue Mar 12 13:30:31 MDT 2013

RAID6 can lose any 2 drives and still operate, so any 3 drives will
cause complete failure.
RAID10 will fail in as few as 2 drive failures, or as much as half of
the array + 1.

RAID10 has a better best case scenario failure rate, but a worse worst
case scenario than RAID6.
It may be unlikely, perhaps even very unlikely, for matched pairs to
fail together, it still must be considered.

This limitation can be mitigated with hot spares since they decrease
the window of time the array is in a degraded state.  Also since
RAID10 has a much quicker rebuild time, the window will be really
small with a hot spare or two.

On Tue, Mar 12, 2013 at 1:10 PM, Nicholas Leippe <nick at leippe.com> wrote:
> On Tue, Mar 12, 2013 at 1:06 PM, Lonnie Olson <lists at kittypee.com> wrote:
>> Important thing to consider is Murphy's law.  The minimum number of
>> disk failures to destroy your whole array.  In RAID6, it's 3 disks.
>> In RAID10, it's 2 disks.  Obviously this would have to be a matched
>> pair, but s#!* happens.
> I haven't studied raid6--how flexible is it regarding which 3 disks
> can fail, compared to raid10's up to half excluding both from a
> mirrored pair?
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