From owner-freebsd-current  Wed Sep 24 07:15:10 1997
Return-Path: <owner-freebsd-current>
Received: (from root@localhost)
          by hub.freebsd.org (8.8.7/8.8.7) id HAA00568
          for current-outgoing; Wed, 24 Sep 1997 07:15:10 -0700 (PDT)
Received: from Octopussy.MI.Uni-Koeln.DE (Octopussy.MI.Uni-Koeln.DE [134.95.166.20])
          by hub.freebsd.org (8.8.7/8.8.7) with SMTP id HAA00553;
          Wed, 24 Sep 1997 07:15:01 -0700 (PDT)
Received: from x14.mi.uni-koeln.de ([134.95.219.124]) by Octopussy.MI.Uni-Koeln.DE with SMTP id AA16883
  (5.67b/IDA-1.5); Wed, 24 Sep 1997 16:12:11 +0200
Received: (from se@localhost) by x14.mi.uni-koeln.de (8.8.7/8.6.9) id QAA01331; Wed, 24 Sep 1997 16:00:22 +0200 (CEST)
X-Face: "<d]#=8pzx);RzeqSKI86OVa7=!0/(uRa.+B.9Z9\eNUn@UG?!`y7yt2dFNn%k4'.}](uE%
 yCO)$e&Y1%3EO~ifu6Q-#YUM&JZ't,}JkPnAz,8Dj33u%@GBi%[Y#LHz$]h7a<p4)-jKI7~sKjlP-^
 EvA[G;]v&0]W!EL%shs,{7x0|oqN4YVIs5,NI#,V{9"WF):5&RkOhyj*#-IAG}Tnu;YCF,d
Message-Id: <19970924160022.50021@mi.uni-koeln.de>
Date: Wed, 24 Sep 1997 16:00:22 +0200
From: Stefan Esser <se@FreeBSD.ORG>
To: Terry Lambert <tlambert@primenet.com>
Cc: dyson@FreeBSD.ORG, syssgm@dtir.qld.gov.au, freebsd-current@FreeBSD.ORG
Subject: Re: New timeout capability (was Re: cvs commit:....)
References: <199709230920.EAA00190@dyson.iquest.net> <199709240617.XAA04899@usr07.primenet.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
X-Mailer: Mutt 0.74
In-Reply-To: <199709240617.XAA04899@usr07.primenet.com>; from Terry Lambert on Wed, Sep 24, 1997 at 06:17:23AM +0000
Sender: owner-freebsd-current@FreeBSD.ORG
X-Loop: FreeBSD.org
Precedence: bulk

On Sep 24, Terry Lambert <tlambert@primenet.com> wrote:
> > I think that 4K performs pretty darned well anyway though.  In the
> > real world, I wouldn't think that one would see much of a performance
> > difference between 4K and 16K. 
> 
> For 8k, there used to be about a 40% improvement over 4k for iozone; I
> haven't really tried this for about 5 moths now, though.

Hmmm, did you measure accesses to the 
char device, block device, or a file ???

If you used the character device, then
the difference is due to processing 
overhead in the drive. But because of
the cluster code, requests for small
data transfers are only sent to the 
drive if the data is fragmented, both
with 4KB and larger block sizes ...

Accesses to the block device should be
mostly independent of the request size.
2KB requests are sent to the drive in
any case ...


I'd be very surprised, if your IOZONE
results were different by 40% for file
accesses (were clustering helps).

Regards, STefan