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List:       linux-kernel
Subject:    Re: Slow disks.
From:       Michael Tokarev <mjt () tls ! msk ! ru>
Date:       2010-12-25 21:28:37
Message-ID: 4D166205.4070205 () msgid ! tls ! msk ! ru
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25.12.2010 21:12, Jaap Crezee wrote:
> On 12/25/10 13:19, Mikael Abrahamsson wrote:
>> On Sat, 25 Dec 2010, Rogier Wolff wrote:
>> Read errors will use parity drive and be re-written by the md layer.
> 
> Can you show us *that* code? I don't recall seeing this behaviour....
> Just one read error and "bang". Or does the kernel not report the first
> few read errors and just continues without telling us?
> I don't like that. With a normal disk without raid I would have had some
> log telling me the disk got bad?

The code is in the md driver.

This behavour is here for several years.  If the drive respond in time
ofcourse - if it tries to re-read the problematic sector forever and
ignores other commands during this time it will be kicked off any
array - be it software or hardware.

The logs will be in whatever logfile your kernel messages are logged to.

And yes, the application which reads the "problematic" area is _not_
notfied, since the data gets restored from other driver - if that was
an md array with sufficient redundancy (any non-degraded raid other
than raid0).

/mjt
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