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Date:      Mon, 25 Aug 2003 02:31:58 +0200
From:      Erik Trulsson <ertr1013@student.uu.se>
To:        Chris Newman <canman@ev1.net>
Cc:        freebsd-questions@FreeBSD.ORG
Subject:   Re: hard disk performance issue
Message-ID:  <20030825003158.GA72370@falcon.midgard.homeip.net>
In-Reply-To: <000001c36a95$bdd637b0$0300a8c0@owl>
References:  <000001c36a95$bdd637b0$0300a8c0@owl>

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On Sun, Aug 24, 2003 at 06:16:11PM -0500, Chris Newman wrote:
> Hi,
> 
> I have a Dell P3-500 Optiplex GX1. I was running FreeBSD 5.0 on an 8G drive.
> I recently upgraded to a Western Digital ATA100 40GB drive and loaded
> FreeBSD 5.1.
> I expected to get improved drive performance, however, my motherboard would
> only do UDMA-33.
> 
> So, I picked up a Maxtor SATA/150 PCI Combo card. It's supposed to do
> ATA-100. My dmesg
> indicates that it is running UDMA-100, but my disk dump performance is still
> pathetic.
> 
> Here's a dd sample:
> 
> tigger# dd if=/dev/ad8s1d of=/home/chris/tmp.dat count=10000
> 10000+0 records in
> 10000+0 records out
> 5120000 bytes transferred in 2.292473 secs (2233396 bytes/sec)
> 
> ~ 2MB per second?? It was about 1.8MB per second before I upgraded. The only
> thing
> I can attribute the marginal speed-up to is the faster drive rotation speed
> (7400 RPM).

What do you expect when you only transfer 512 bytes with each
read/write? That is a lot of overhead, and will make the actual speed
of the disk to have little effect on the numbers obtained.

Try increasing the block size. I.e. try:

dd if=/dev/ad8s1d of=/home/chris/tmp.dat bs=64k count=100

On my system that gives about a factor of 8 faster performance.
To get a better idea on how fast the disk actually is (with less
overhead from the filesystem, and with less seeking involved) (and also
to get bigger numbers :-) ) try sending the output to /dev/null instead
of an actual file. (I.e. use of=/dev/null instead of of=/home/chris/tmp.dat)

-- 
<Insert your favourite quote here.>
Erik Trulsson
ertr1013@student.uu.se



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