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Date:      Sat, 30 Nov 1996 12:57:43 -0100
From:      Darius Moos <moos@degnet.baynet.de>
To:        "John S. Dyson" <toor@dyson.iquest.net>
Cc:        mango@staff.communique.net, hackers@freefall.freebsd.org, hardware@freefall.freebsd.org
Subject:   Re: Adaptec UW controller and Seagate Elite performance ?
Message-ID:  <32A03D57.6274@degnet.baynet.de>
References:  <199611300444.XAA09675@dyson.iquest.net>

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One thing that stroke me some time ago was the termination of the
SCSI-bus. After changing from passive to active termination, the
speed of my disks doubled !!!

Darius Moos.


John S. Dyson wrote:
> 
> >
> > # bonnie -s 40        (akira, http running)
> >    -------Sequential Output-------- ---Sequential Input-- --Random--
> >    -Per Char- --Block--- -Rewrite-- -Per Char- --Block--- --Seeks---
> > MB K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU  /sec %CPU
> > 40  3271 34.8  3085 13.0  1559  8.3 10330 97.1 44763 95.7 991.0 20.4
> >
> > and
> > IOZONE performance measurements:
> >         2039008 bytes/second for writing the file
> >         34861747 bytes/second for reading the file
> >
> > It bothered me that:
> > 1- reading is 20 times faster than writing
> 
> You are seeing the results of caching.  The system remembers what
> is written so that it doesn't have to unnecessarily re-read the
> data.
> 
> >
> > 2- 2Mbytes/s for writing seems slow, even if this was a scsi-2 and not
> > an
> > scsi fast and wide drive.
> >
> I don't know why your iozone write perf is so slow, unless you are writing
> 512 bytes at a time.  Note also, that you might not have the write
> behind caching enabled on your drive.
> 
> Try the following commands:
> 
> # iozone auto
> and
> # iozone 40 8192
> and
> # iozone <size-of-memory*2> 8192
> 
> and let me know the results.
> 
> John
> dyson@freebsd.org



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