From: Max Waterman <davidmaxwaterman+kernel@fastmail.co.uk>
To: Phillip Susi <psusi@cfl.rr.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: io performance...
Date: Fri, 20 Jan 2006 13:58:32 +0800 [thread overview]
Message-ID: <43D07C08.5000903@fastmail.co.uk> (raw)
In-Reply-To: <43CE5C7A.5060608@cfl.rr.com>
Phillip Susi wrote:
> Right, the kernel does not know how many disks are in the array, so it
> can't automatically increase the readahead. I'd say increasing the
> readahead manually should solve your throughput issues.
Any guesses for a good number?
We're in RAID10 (2+2) at the moment on 2.6.8-smp. These are the block
numbers I'm getting using bonnie++ :
ra wr rd
256 68K 46K
512 67K 59K
640 67K 64K
1024 66K 73K
2048 67K 88K
3072 67K 91K
8192 71K 96K
9216 67K 92K
16384 67K 90K
I think we might end up going for 8192.
We're still wondering why rd performance is so low - seems to be the
same as a single drive. RAID10 should be the same performance as RAID0
over two drives, shouldn't it?
Max.
>
> Max Waterman wrote:
>>
>> I left the stripe size at the default, which, I believe, is 64K bytes;
>> same as your fakeraid below.
>>
>> I did play with 'blockdev --setra' too.
>>
>> I noticed it was 256 with a single disk, and, with s/w raid, it
>> increased by 256 for each extra disk in the array. IE for the raid 0
>> array with 4 drives, it was 1024.
>>
>> With h/w raid, however, it did not increase when I added disks. Should
>> I use 'blockdev --setra 320' (ie 64 x 5 = 320, since we're now running
>> RAID5 on 5 drives)?
>>
>
next prev parent reply other threads:[~2006-01-20 5:58 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-01-16 7:35 io performance Max Waterman
2006-01-16 7:32 ` Jeff V. Merkey
2006-01-17 13:57 ` Jens Axboe
2006-01-17 19:17 ` Jeff V. Merkey
2006-01-16 8:35 ` Pekka Enberg
2006-01-17 17:06 ` Phillip Susi
2006-01-18 7:24 ` Max Waterman
2006-01-18 15:19 ` Phillip Susi
2006-01-20 5:58 ` Max Waterman [this message]
2006-01-20 13:42 ` Ian Soboroff
2006-01-25 6:36 ` Max Waterman
2006-01-25 14:19 ` Ian Soboroff
2006-01-25 13:09 ` Bernd Eckenfels
2006-01-18 3:02 ` Max Waterman
2006-01-18 4:30 ` Jeff V. Merkey
2006-01-18 5:09 ` Max Waterman
2006-01-18 4:37 ` Jeff V. Merkey
2006-01-18 7:06 ` Max Waterman
2006-01-18 9:21 ` Alan Cox
2006-01-18 15:48 ` Phillip Susi
2006-01-18 16:25 ` Bartlomiej Zolnierkiewicz
2006-01-19 0:48 ` Adrian Bunk
2006-01-19 13:18 ` Max Waterman
[not found] <5vx8f-1Al-21@gated-at.bofh.it>
[not found] ` <5wbRY-3cF-3@gated-at.bofh.it>
[not found] ` <5wdKh-5wF-15@gated-at.bofh.it>
2006-01-19 1:58 ` Robert Hancock
2006-01-19 13:14 ` Max Waterman
2006-01-19 14:08 ` Alan Cox
2006-01-20 4:09 ` Max Waterman
2006-01-20 4:27 ` Alexander Samad
2006-01-20 12:52 ` Alan Cox
2006-01-19 11:39 Al Boldi
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