matthew at FreeBSD.org
Wed Apr 20 09:23:49 UTC 2016
On 04/19/16 22:43, Lowell Gilbert wrote:
> Correlation is not causation.
> It's not a big stretch to imagine that two nearly identical mechanical
> devices, operated in nearly identical conditions, might wear out in a
> nearly identical way at about the same time. There is no need for one
> drive to affect the other.
Interestingly this argument is quite a bit stronger when applied to
SSD's rather than spinning disk drives. SSDs we know have a limited
number of refresh cycles for any one memory cell. As members of a RAID
array, they're going to see very similar patterns of activity over their
lifetimes, so they're actually quite likely to wear out at a similar time.
> A fair number of people believe that this in fact occurs. I've looked
> for evidence on the subject, and I haven't found anything (beyond
> anecdotes) for or against the possibility.
Mechanical drives are a lot more affected by external differences like
vibration or temperature changes, which will act to increase the
variability in their lifetimes. SSDs are intrinsically /more/ reliable
during their working life, but their lifetime tends to come to a much
more sharply defined end.
Matthew (who has been spending far too much time going to the
datacentre to replace drives recently.)
-------------- next part --------------
A non-text attachment was scrubbed...
Size: 801 bytes
Desc: OpenPGP digital signature
More information about the freebsd-questions