From: Al Boldi <a1426z@gawab.com>
To: Willy Tarreau <willy@w.ods.org>
Subject: Re: Eradic disk access during reads
Date: Sat, 17 Sep 2005 13:32:53 +0300
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Willy Tarreau wrote:
> On Sat, Sep 17, 2005 at 07:26:11AM +0300, Al Boldi wrote:
> > Monitoring disk access using gkrellm, I noticed that a command like
> >
> > cat /dev/hda > /dev/null
> >
> > shows eradic disk reads ranging from 0 to 80MB/s on an otherwise idle
> > system.
> >
> > 1. Is this a hardware or software problem?
>
> Difficult to tell without more info. Can be a broken IDE disk or defective
> ribbon.

Tried the same with 2.4.31 which shows steady behaviour with occasional dips 
and pops in the msec range.

>
> > 2. Is there a lightweight perf-mon tool (cmd-line) that would log this
> > behaviour graphically?
>
> You can do " readspeed </dev/hda | tr '\r' '\n' > log " with the readspeed
> tool from there :
>    http://w.ods.org/tools/readspeed

Does it have msec resolution?

Thanks!

--
Al
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