From: Ming Zhang <mingz@ele.uri.edu>
To: Mirko Benz <mirko.benz@web.de>
Cc: Neil Brown <neilb@cse.unsw.edu.au>,
Linux RAID <linux-raid@vger.kernel.org>
Subject: Re: RAID 5 write performance advice
Date: Fri, 26 Aug 2005 13:05:23 -0400 [thread overview]
Message-ID: <1125075923.5549.61.camel@localhost.localdomain> (raw)
In-Reply-To: <430F3565.2070302@web.de>
i think this is out of my mind now. i think 4+1 DISK with 64KB chunk
size is 256KB which fit the 1M size well. So there should not have any
read happen...
ming
On Fri, 2005-08-26 at 17:29 +0200, Mirko Benz wrote:
> Hello,
>
> Here are the results using 5 disks for RAID 5 – basically the same
> results but with lower values.
> Again, much slower than it could be.
>
> *** dd TEST ***
>
> time dd if=/dev/zero of=/dev/md0 bs=1M
> 2819620864 bytes transferred in 23,410720 seconds (120441442 bytes/sec)
>
> iostat 5 output:
> avg-cpu: %user %nice %sys %iowait %idle
> 0,10 0,00 55,40 36,20 8,30
>
> Device: tps Blk_read/s Blk_wrtn/s Blk_read Blk_wrtn
> hda 0,00 0,00 0,00 0 0
> sda 0,00 0,00 0,00 0 0
> sdb 345,09 1999,20 71501,40 9976 356792
> sdc 348,10 2412,83 71434,07 12040 356456
> sdd 356,31 2460,92 71748,30 12280 358024
> sde 351,50 2456,11 71058,92 12256 354584
> sdf 348,10 2008,82 70935,47 10024 353968
> sdg 0,00 0,00 0,00 0 0
> sdh 0,00 0,00 0,00 0 0
> sdi 0,00 0,00 0,00 0 0
> sdj 0,00 0,00 0,00 0 0
> sdk 0,00 0,00 0,00 0 0
> sdl 0,00 0,00 0,00 0 0
> sdm 0,00 0,00 0,00 0 0
> sdn 0,00 0,00 0,00 0 0
> md0 35226,65 0,00 281813,23 0 1406248
>
> disktest gives 99 MB/s but shows the same behaviour (unbalanced usage of
> disks).
>
> Regards,
> Mirko
>
> Ming Zhang schrieb:
>
> >i would like to suggest u to do a 4+1 raid5 configuration and see what
> >happen.
> >
> >Ming
> >
> >On Fri, 2005-08-26 at 09:51 +0200, Mirko Benz wrote:
> >
> >
> >>Hello,
> >>
> >>We have created a RAID 0 for the same environment:
> >>Personalities : [raid0] [raid5]
> >>md0 : active raid0 sdi[7] sdh[6] sdg[5] sdf[4] sde[3] sdd[2] sdc[1] sdb[0]
> >> 1250326528 blocks 64k chunks
> >>
> >>*** dd TEST ***
> >>
> >>time dd if=/dev/zero of=/dev/md0 bs=1M
> >>14967373824 bytes transferred in 32,060497 seconds (466847843 bytes/sec)
> >>
> >>iostat 5 output:
> >>avg-cpu: %user %nice %sys %iowait %idle
> >> 0,00 0,00 89,60 9,50 0,90
> >>
> >>Device: tps Blk_read/s Blk_wrtn/s Blk_read Blk_wrtn
> >>hda 0,00 0,00 0,00 0 0
> >>sda 0,00 0,00 0,00 0 0
> >>sdb 455,31 0,00 116559,52 0 581632
> >>sdc 455,51 0,00 116540,28 0 581536
> >>sdd 450,10 0,00 116545,09 0 581560
> >>sde 454,11 0,00 116559,52 0 581632
> >>sdf 452,30 0,00 116559,52 0 581632
> >>sdg 454,71 0,00 116553,11 0 581600
> >>sdh 453,31 0,00 116533,87 0 581504
> >>sdi 453,91 0,00 116556,31 0 581616
> >>sdj 0,00 0,00 0,00 0 0
> >>sdk 0,00 0,00 0,00 0 0
> >>sdl 0,00 0,00 0,00 0 0
> >>sdm 0,00 0,00 0,00 0 0
> >>sdn 0,00 0,00 0,00 0 0
> >>md0 116556,11 0,00 932448,90 0 4652920
> >>
> >>Comments: 466 MB / 8 = 58,25 MB/s which is about the same as a dd to a
> >>single disk (58,5 MB/s). So the controller + I/O subsystem is not the
> >>bottleneck.
> >>
> >>Regards,
> >>Mirko
> >>
> >>
> >>
> >
> >
> >
> >
>
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next prev parent reply other threads:[~2005-08-26 17:05 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-08-24 8:24 RAID 5 write performance advice Mirko Benz
2005-08-24 12:46 ` Ming Zhang
2005-08-24 13:43 ` Mirko Benz
2005-08-24 13:49 ` Ming Zhang
2005-08-24 21:32 ` Neil Brown
2005-08-25 16:38 ` Mirko Benz
2005-08-25 16:54 ` Ming Zhang
2005-08-26 7:51 ` Mirko Benz
2005-08-26 14:26 ` Ming Zhang
2005-08-26 14:30 ` Ming Zhang
2005-08-26 15:29 ` Mirko Benz
2005-08-26 17:05 ` Ming Zhang [this message]
2005-08-28 23:28 ` Neil Brown
2005-09-01 19:44 ` djani22
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