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Date:      Wed, 2 Apr 2003 11:13:26 +0930
From:      Greg 'groggy' Lehey <grog@FreeBSD.org>
To:        Jason Andresen <jandrese@mitre.org>
Cc:        FreeBSD Stable List <freebsd-stable@freebsd.org>
Subject:   Re: vinum performance
Message-ID:  <20030402014326.GJ34617@wantadilla.lemis.com>
In-Reply-To: <3E89A0DE.7040505@mitre.org>
References:  <20030330125138.K23911@leelou.in.tern> <3E870CC7.5000204@mac.com> <20030330175605.E23911@leelou.in.tern> <3E87204C.5060304@ludd.luth.se> <3E88524A.1060600@mitre.org> <3E88AECD.10607@liwing.de> <3E88B601.90802@mitre.org> <20030401004953.GE34617@wantadilla.lemis.com> <3E89A0DE.7040505@mitre.org>

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On Tuesday,  1 April 2003 at  9:23:26 -0500, Jason Andresen wrote:
> Greg 'groggy' Lehey wrote:
>
>>>>> I get 4565 K/sec on modern ATA/133 HDDs.
>>>>>
>>>>> Reading is much better at 91908 K/sec at least.
>>>
>>> Well, I'm writing 200MB files most of the time, so the stripe size is
>>> not an issue.  I'm just wondering why the reads are *20* times faster
>>> than the writes.
>>
>>
>> They're not.  I don't know where you get that read figure from, but no
>> disk can transfer that fast, and you don't appear to be doing multiple
>> transfers in parallel.
>
> That was what bonnie++ reported.

As I've said elsewhere, bonnie++ is not an appropriate benchmark here.

>>> I think the read performance was CPU limited in this case.
>>
>>
>> I think you were reading from cache.
>
> Quite possible.  I'm not sure how bonnie handles that.

It reads from cache.

Greg
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