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Message-ID: <19971108114521.06151@mi.uni-koeln.de>
Date: Sat, 8 Nov 1997 11:45:21 +0100
From: Stefan Esser <se@FreeBSD.ORG>
To: Amancio Hasty <hasty@rah.star-gate.com>
Cc: hackers@FreeBSD.ORG
Subject: Re: Seagate Cheetah performance...
References: <199711080104.RAA00593@rah.star-gate.com> <199711080626.WAA08424@rah.star-gate.com>
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In-Reply-To: <199711080626.WAA08424@rah.star-gate.com>; from Amancio Hasty on Fri, Nov 07, 1997 at 10:26:34PM -0800
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On 1997-11-07 22:26 -0800, Amancio Hasty <hasty@rah.star-gate.com> wrote:
> Well, 
> 
> I found a way to nearly double my performance:
> 
> 
>  iozone 48
> 
>         IOZONE: Performance Test of Sequential File I/O  --  V2.01 (10/21/94)
>                 By Bill Norcott
> 
>         Operating System: FreeBSD 2.x -- using fsync()
> 
>         Send comments to:       b_norcott@xway.com
> 
>         IOZONE writes a 48 Megabyte sequential file consisting of
>         98304 records which are each 512 bytes in length.
                                       ^^^^^^^^^ This is where 
				       your problem originates!

Reading 512 byte blocks is not a typical situation at all ...

>         It then reads the file.  It prints the bytes-per-second
>         rate at which the computer can read and write files.
> 
> 
> Writing the 48 Megabyte file, 'iozone.tmp'...5.523438 seconds
> Reading the file...4.921875 seconds
> 
> IOZONE performance measurements:
>         9112377 bytes/second for writing the file
>         10226112 bytes/second for reading the file

This is > 20000 SCSI commands ! SCSI overhead must be lower than 50us !
Wow! What are you complaining about ? :-)

> > Any tweaking that I do to improve the performance of my :
> >  <SEAGATE ST34501W 0017> type 0 fixed SCSI 2
> > 
> >  iozone 48

> > IOZONE performance measurements:
> >         5418377 bytes/second for writing the file
> >         7828008 bytes/second for reading the file

Again: You are using a much to small transfer rate !

> > My Ultra DMA IDE disk generates about 8MB/sec for writing .

IDE overhead is much smaller than SCSI, there is no arbitration 
for a shared bus, for example.


Please test all three drives with Bonnie. Use a test file at 
least twice as much as your system's RAM, and report your 
findings ...

You'll get a different picture, I assume !

Regards, STefan