Re: high load on heavy disk i/o (fwd)

Gerard Roudier (groudier@club-internet.fr)
Wed, 29 Sep 1999 22:09:50 +0200 (MET DST)

The FS block size is not a driver issue. The command you use (cat
/dev/zero > some_file) is an extremally high stress for the caching policy
in some Linux kernel versions. Based on the fiew information your report,
I donnot see any obvious problems related to the SCSI sub-system. Did you
look into the system log to see if some not usual messages were written
during that IO load that seems to you not normal?

Gérard.

On Wed, 29 Sep 1999, Ronald Wahl wrote:

> Maybe its not scsi related - so i repost this here...
>
> ---------- Forwarded message ----------
> Date: Tue, 28 Sep 1999 03:47:45 +0200 (CEST)
> From: Ronald Wahl <rwahl@gmx.net>
> To: linux-scsi <linux-scsi@vger.rutgers.edu>
> Subject: Re: high load on heavy disk i/o
>
> On Mon, 27 Sep 1999, Ronald Wahl wrote:
>
> > Hi,
> >
> > after installing a new disk (IBM DNES-309170W U2W SE/LVD - was cheaper
> > than the UW model :-) on my SYMBIOS Controller (sym53c875 rev. 4). I
> > noticed that during heavy disk i/o (e.g. creating a cdrom image or doing
> > "cat /dev/zero > some_file") the load goes up to 3 or more and the system
> > becomes totally unusable. Mostly all programs called during this time
> > starting after the i/o load is gone. First I thought it was the cable
> > length since it was 2m in length and ultra scsi spec doesn't allow greater
> > than 1.5m in my case. Both ends are are terminated (active). I even had
> > some wrong data during transfer (but very seldom). So I shorted my narrow
> > cable to fit the spec. But at least the problem with the heavy load and
> > system unusability is still there. Without this new disk I had no such
> > problems. What's the problem here?
> > <...>
>
> The following may be relevant: mke2fs created most of my partions with a
> blocksize of 4096 bytes (which seems to speed things greatly up!). Maybe
> the driver has a problem with this greater blocks. I have similar
> problems (high load, system unusable) with my MO drive which uses 2048
> byte blocks (even under 2.0.36 this was a problem).
>
> ron
>
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