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Date: Fri, 10 Nov 2006 12:09:37 +1300
From: Mark Kirkwood <markir@paradise.net.nz>
In-reply-to: <E1Gi8I0-0006I7-Dk@dilbert.firstcallgroup.co.uk>
To: Pete French <petefrench@ticketswitch.com>
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Cc: freebsd-stable@FreeBSD.ORG
Subject: Re: Dissapointing performance of ciss RAID 0+1 ?
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Pete French wrote:
>> You might be able to speed up the read by playing with the vfs.read_max 
>> sysctl (try 16 or 32).
> 
> Wow! That makes a huge difference, thanks. Should this not be in 'man tuning' ?
> 

Yeah, I believe I've seen it mentioned *somewhere* with respect to 
working with RAID (of course, I can't find it now....).

The other thing you might find useful for improving sequential 
performance is using newfs options '-b 32768 -f 4096' - I've found it 
produces a noticeable performance improvement (can't recall exactly but 
in the region of 10%).

I'm using an older system (3ware 7506 + 4 7200 rpm disks RAID 0 256 K 
stripe), and with the above newfs settings + vfs.read_max=16 I get about 
190Mb/s for 8k reads and 160Mb/s for 8k writes (sustained for quite big 
files e.g. 16Gb). This is on 6.2 PRERELEASE, and I'm pretty happy with 
that level of performance (nice job to those of you who have been 
steadily making 6-STABLE go faster....)!

Cheers

Mark