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Re: Negligible improvement when using su/sw for hardware RAID5, expected

To: utz lehmann <u.lehmann@xxxxxxxxxxxxxx>
Subject: Re: Negligible improvement when using su/sw for hardware RAID5, expected?
From: Brian Davis <bridavis@xxxxxxxxxxx>
Date: Mon, 14 Aug 2006 09:29:42 -0400
Cc: xfs@xxxxxxxxxxx
In-reply-to: <1155545494.1238.11.camel@donner.tecosim.de>
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I'll admit to being ignorant here....all I did was created the Linux partition with fdisk and then created the fs on top of that. Was there something else that needed to be done?

Thanks,
Brian

utz lehmann wrote:
Hi

You are using a partition. Is it correctly aligned? Usually the first
partition starts at sector 63. Which is in the middle of your stripe.
Use the whole disk (/dev/sda) or align the start of the partition to a
multiple of the stripe size.
But i doubt you will see a performance improvement with such a simple
test (single threaded sequential read/ write).


utz


On Fri, 2006-08-11 at 23:10 -0400, Brian Davis wrote:
Is this expected? I thought I would see more improvement when tweaking my su/sw values for hardware RAID 5.

Details, 3x300GB drives, 3Ware 7506-4LP Hardware RAID 5 using a 64K stripe size (non-configurable on this card).

FS creation and Bonnie++ results:

Untweaked:----------------------------------------------------------------------


localhost / # mkfs.xfs -f /dev/sda1
meta-data=/dev/sda1 isize=256 agcount=32, agsize=4578999 blks
= sectsz=512 attr=0
data = bsize=4096 blocks=146527968, imaxpct=25
= sunit=0 swidth=0 blks, unwritten=1
naming =version 2 bsize=4096
log =internal log bsize=4096 blocks=32768, version=1
= sectsz=512 sunit=0 blks
realtime =none extsz=65536 blocks=0, rtextents=0
localhost / # mount -t xfs /dev/sda1 /raid
localhost / # cd /raid
localhost raid # bonnie++ -n0 -u0 -r 768 -s 30720 -b -f
Using uid:0, gid:0.
Writing intelligently...done
Rewriting...done
Reading intelligently...done
start 'em...done...done...done...done...done...
Version 1.93c ------Sequential Output------ --Sequential Input- --Random-
Concurrency 1 -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec %CP
localhost 30G 27722 40 23847 37 98367 99 88.6 11
Latency 891ms 693ms 16968us 334ms


Tweaked:-------------------------------------------------------------------------


localhost / # mkfs.xfs -f -d sw=2,su=64k /dev/sda1
meta-data=/dev/sda1 isize=256 agcount=32, agsize=4578992 blks
= sectsz=512 attr=0
data = bsize=4096 blocks=146527744, imaxpct=25
= sunit=16 swidth=32 blks, unwritten=1
naming =version 2 bsize=4096
log =internal log bsize=4096 blocks=32768, version=1
= sectsz=512 sunit=0 blks
realtime =none extsz=65536 blocks=0, rtextents=0
localhost / # mount -t xfs /dev/sda1 /raid
localhost / # cd /raid
localhost raid # bonnie++ -n0 -u0 -r 768 -s 30720 -b -f
Using uid:0, gid:0.
Writing intelligently...done
Rewriting...done
Reading intelligently...done
start 'em...done...done...done...done...done...
Version 1.93c ------Sequential Output------ --Sequential Input- --Random-
Concurrency 1 -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec %CP
localhost 30G 27938 43 23880 40 98066 99 91.8 9
Latency 772ms 584ms 19889us 340ms




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