[mythtv-users] 2 TB Hard Drive Recommendations
Simon Hobson
linux at thehobsons.co.uk
Mon Dec 6 07:54:47 UTC 2010
Jean-Yves Avenard wrote:
>so two drives out of 6 dying in 18 months, so close to each other
>isn't that great.
That's one of the problems where the idea of RAID breaks down. You
buy a set of disks (same make and model, possibly even from the same
manufacturing batch), stuff them in an enclosure, and run them for
the same power on hours, doing the same usage profile - ie they are
run under near identical conditions. That means the failures are
liable to be less distributed temporally than you might be thinking.
So you've massively increased the chance of two (or more)
simultaneous failures.
I saw that in one of our Unix servers at my last job. A drive failed,
and it took our maintainers a while to get a replacement because they
struggled to understand that they can't supply any old "9GB drive"
and it must be at least the same number of blocks as the smallest in
the array. By the time it did get replaced, two more were showing an
increasing error count and I think we replaced 3 in an array of 4 !
For that reason, I've always setup my arrays to use a bit less than
the full disk to allow for a slightly smaller drive as a replacement.
So I think there is an argument (if possible) to at least spread your
purchases and build the array over several months - if you use all
the same drive, that should at least give you a chance of them coming
from different batches and reduce the chance of a common defect.
--
Simon Hobson
Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed
author Gladys Hobson. Novels - poetry - short stories - ideal as
Christmas stocking fillers. Some available as e-books.
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