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From: "Jaime Bozza" <wheelman@nuc.net>
To: "Mike Smith" <mike@smith.net.au>, "Berend de Boer" <berend@pobox.com>
Cc: <stable@FreeBSD.ORG>
Subject: RE: best sd0 flags ? (was wdc0) 
Date: Mon, 20 Apr 1998 10:01:32 -0500
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> As Bruce mentioned, you should use the raw device:
>
> azaria# dd if=/dev/sd1 of=/dev/null bs=1m count=20
> 20+0 records in
> 20+0 records out
> 20971520 bytes transferred in 9.182458 secs (2283868 bytes/sec)
> azaria# dd if=/dev/rsd1 of=/dev/null bs=1m count=20
> 20+0 records in
> 20+0 records out
> 20971520 bytes transferred in 2.571084 secs (8156684 bytes/sec)
>
> for a similar configuration (DCAS34330UW, PII/337, AHA2940UW)

I decided to try the same thing.  Always been curious about the performance.

%dd if=/dev/sd0 of=/dev/null bs=1m count=20
20+0 records in
20+0 records out
20971520 bytes transferred in 4.835489 secs (4337001 bytes/sec)
%dd if=/dev/rsd0 of=/dev/null bs=1m count=20
20+0 records in
20+0 records out
20971520 bytes transferred in 2.201617 secs (9525508 bytes/sec)

I did it a few times, and have seen slightly higher and slightly lower.  9M
seems to be about an average for me.

That particular system is a SEAGATE ST34555W 0930 (Seagate Hawk), Pentium
133, Adaptec 2940W (Not a(n) UW, though the drive is an UltraWide)

Another system with a 2940UW/P5-133/SEAGATE ST15150W 0011  (One of the
original Seagate Barracudas!)

meson# dd if=/dev/sd0 of=/dev/null bs=1m count=20
20+0 records in
20+0 records out
20971520 bytes transferred in 8.065788 secs (2600058 bytes/sec)
meson# dd if=/dev/rsd0 of=/dev/null bs=1m count=20
20+0 records in
20+0 records out
20971520 bytes transferred in 3.049587 secs (6876839 bytes/sec)


Jaime Bozza
Nucleus Communications, Inc.


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