[Gllug] Discs for a RAID1 pair

Martin A. Brooks martin at hinterlands.org
Mon Jul 4 17:22:35 UTC 2011

On Mon, July 4, 2011 17:37, - Tethys wrote:
> Don't use two of the same type of drive in your array. That avoids bad
> batch problems where both drives fail simultaneously.

If he's using a proper RAID controller or disk chassis then they're likely
to be somewhat picky about that kind of thing.

I would bet that I've dealt with more large storage than anyone else on
the list (2.5P) and the scenario you've said simply does not happen where
data matters.  Where data matters you're not running RAID1, you're running
RAID10 where speed is important and a variant of RAID6 where it doesn't.
And you're running with a hot spare, probably 2.  And you have backups. 
And we all know that it's not a backup until you've restored from it.  And
we haven't confused "backups" with "near-line copies".

If you're considering using RAID1 because you're worried about data loss,
then you simply haven't understood the problem.

For the record, I do run a RAID1 set for my "big data disk", on identical
disks. I think the serial numbers are even sequential.  I don't give a
crap about the likelyhood, or not, of both disks failing at the same time
because the most I will ever lose is 12 hours of data.  That's a perfectly
acceptable risk for me.  I use RAID1 because it slightly reduces the
chance I will have to actually restore from my backups, and my time is
more valuable.

I know my personal backup strategy works because I restore from it, in
full, twice a year.

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