Re: Read errors on raid5 ignored, array still clean .. then disaster !!

[Luca Berra <bluca@comedia.it>]

On Fri, Jan 29, 2010 at 09:48:52PM +1100, Neil Brown wrote:
>On Wed, 27 Jan 2010 08:41:38 +0100
>Luca Berra <bluca@comedia.it> wrote:
>
>> On Tue, Jan 26, 2010 at 11:28:03PM +0100, Giovanni Tessore wrote:
>> > Is this some kind of bug?  
>> No
>
>
>I'm not sure I agree.
>If a device is generating lots of read errors, we really should do something
>proactive about that.
>If there is a hot spare, then building onto that while keeping the original
>active (yes, still on the todo list) would be a good thing to do.
>
>v1.x metadata allows the number of corrected errors to be recorded across
>restarts so a real long-term value can be used as a trigger.
uhm, should we use an absolute value here, or should we consider the
ratio of read errors over time. Or both?
the former would indicate a disk that is degrading slowly over time
the latter migh be a symptom of a disk that will die very soon.
we also need to control the threshold on a per device base via sysfs
(eg mdX/md/dev-FOO/maximum_tolerated_read_errors)

>So there certainly are useful improvements that could be made here.
I don't deny that, but i would not define as bugs features that are not
yet designed/implemented.

L.


-- 
Luca Berra -- bluca@comedia.it
         Communication Media & Services S.r.l.
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