Subject: Re: Low AAC performance but only when tested through the file system
To: Olaf Seibert <>
From: Bill Studenmund <>
List: current-users
Date: 11/30/2003 15:07:33
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On Sat, Nov 29, 2003 at 03:45:00PM +0100, Olaf Seibert wrote:
> On Fri 28 Nov 2003 at 19:25:05 -0800, Bill Studenmund wrote:
> > > So it's not like the card is not capable of proper transfer counts and
> > > speeds, it seems it is held back somehow by the file system or buffer
> > > cache.
> >=20
> > What is the setup of your raid volume?
> We have a RAID-5 of 5 U-320 SCSI disks of about 35 G each, and one hot
> spare. I have also attached the dmesg output and the disklabel.

What's your stripe depth? For optimal performance, you want it to be 16k. =
The file system will do 64k i/o's. With 4 data drives & a 16k stripe
depth, a 64k i/o (on a 64k boundary) will hit all 4 drives at once.

Take care,


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