Date: Sat, 17 Sep 2005 07:50:10 +0200
From: Willy Tarreau <willy@w.ods.org>
To: Al Boldi <a1426z@gawab.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: Eradic disk access during reads
Message-ID: <20050917055010.GG30279@alpha.home.local>
References: <200509170717.03439.a1426z@gawab.com>
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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.

> 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

Then you just have to graph $6 (kB/s) versus $1 (bytes read). There may
be other tools which do all this automatically though.

Regards,
Willy

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