hard drive performance

Chris Rees utisoft at googlemail.com
Wed Apr 15 16:52:55 UTC 2009

2009/4/15 Bruce Cran <bruce at cran.org.uk>:
> On Wed, 15 Apr 2009 13:54:13 +0200 (CEST)
> Alexander Best <alexbestms at math.uni-muenster.de> wrote:
>> hi there,
>> i have 2 hard drives running. the first one is SATA300 and the other
>> one UDMA100. here are the dmesg entries:
>> ad0: 238474MB <SAMSUNG SP2504C VT100-50> at ata0-master SATA300
>> ad1: 157066MB <Hitachi HDS722516VLAT80 V34OA63A> at ata4-master
>> UDMA100
>> i've tried to test the drives' performances using the following
>> commands:
>> dd if=/dev/ad0 of=/dev/null bs=1m count=300
>> and
>> dd if=/dev/ad1 of=/dev/null bs=1m count=300
>> the results are:
>> ad0 = 314572800 bytes transferred in 4.325645 secs (72722751
>> bytes/sec) ad1 = 314572800 bytes transferred in 5.166126 secs
>> (60891430 bytes/sec)
>> the results for ad0 are a bit disappointing though. is this normal or
>> is bs=1m wrong?
> 70MB/s is a very good transfer rate for a hard drive. The 300MB/s rate
> refers to the maximum the physical interface can support, but drives
> never get close to that because they can't read from disk at that
> speed.
> --
> Bruce Cran

Hehe, I think everyone makes that mistake when they're enthusiastic
and sometimes even somewhat experienced. It's always such a
disappointment when they realise, I remember when I did too.


A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?
A: Top-posting.
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