Raid 1+0

[Jack L.]

On Tue, Apr 19, 2016 at 2:43 PM, Lowell Gilbert
<freebsd-questions-local at be-well.ilk.org> wrote:
> "Valeri Galtsev" <galtsev at kicp.uchicago.edu> writes:
>
>> On Tue, April 19, 2016 9:38 am, Steve O'Hara-Smith wrote:
>>> On Mon, 18 Apr 2016 17:05:22 -0500 (CDT)
>>> "Valeri Galtsev" <galtsev at kicp.uchicago.edu> wrote:
>>>
>>>> Not correct. First of all, in most of the cases, failure of each of the
>>>> drives are independent events
>>>
>>>      If only that were so. When the drives are as near identical as
>>> manufacturing can make them and have had very similar histories they
>>> can be expected to have very similar wear and be similarly close to
>>> failure at all times, which makes it likely that the load imposed by
>>> one failing will push another over.
>>
>> Sigh. You need suggest some physics that will make one drive affect
>> another (aged or not aged doesn't matter for me). Then you will have me in
>> your team.
>
> 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.
>
> 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.

I think all hard drives are garbage and can die at any unpredictable
time. Doesn't matter what brand, what model, what type, they all die
unexpectedly. With that, I just make sure I have good backups just in
case there's multiple drive failures in a raid set.