From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ming Zhang Subject: Re: RAID 5 write performance advice Date: Fri, 26 Aug 2005 13:05:23 -0400 Message-ID: <1125075923.5549.61.camel@localhost.localdomain> References: <430C2EA6.2050103@web.de> <1124887589.5550.27.camel@localhost.localdomain> <430C798B.1030107@web.de> <17164.59261.540591.841830@cse.unsw.edu.au> <430DF416.1070101@web.de> <1124988876.5552.59.camel@localhost.localdomain> <430ECA18.10405@web.de> <1125066621.5549.27.camel@localhost.localdomain> <430F3565.2070302@web.de> Reply-To: mingz@ele.uri.edu Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <430F3565.2070302@web.de> Sender: linux-raid-owner@vger.kernel.org To: Mirko Benz Cc: Neil Brown , Linux RAID List-Id: linux-raid.ids 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...=20 ming On Fri, 2005-08-26 at 17:29 +0200, Mirko Benz wrote: > Hello, >=20 > Here are the results using 5 disks for RAID 5 =E2=80=93 basically the= same=20 > results but with lower values. > Again, much slower than it could be. >=20 > *** dd TEST *** >=20 > time dd if=3D/dev/zero of=3D/dev/md0 bs=3D1M > 2819620864 bytes transferred in 23,410720 seconds (120441442 bytes/se= c) >=20 > iostat 5 output: > avg-cpu: %user %nice %sys %iowait %idle > 0,10 0,00 55,40 36,20 8,30 >=20 > 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 >=20 > disktest gives 99 MB/s but shows the same behaviour (unbalanced usage= of=20 > disks). >=20 > Regards, > Mirko >=20 > Ming Zhang schrieb: >=20 > >i would like to suggest u to do a 4+1 raid5 configuration and see wh= at > >happen. > > > >Ming > > > >On Fri, 2005-08-26 at 09:51 +0200, Mirko Benz wrote: > > =20 > > > >>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=3D/dev/zero of=3D/dev/md0 bs=3D1M > >>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_w= rtn > >>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 0 581= 632 > >>sdc 455,51 0,00 116540,28 0 581= 536 > >>sdd 450,10 0,00 116545,09 0 581= 560 > >>sde 454,11 0,00 116559,52 0 581= 632 > >>sdf 452,30 0,00 116559,52 0 581= 632 > >>sdg 454,71 0,00 116553,11 0 581= 600 > >>sdh 453,31 0,00 116533,87 0 581= 504 > >>sdi 453,91 0,00 116556,31 0 581= 616 > >>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 0 465= 2920 > >> > >>Comments: 466 MB / 8 =3D 58,25 MB/s which is about the same as a dd= to a=20 > >>single disk (58,5 MB/s). So the controller + I/O subsystem is not t= he=20 > >>bottleneck. > >> > >>Regards, > >>Mirko > >> > >> =20 > >> > > > > > > =20 > > >=20 - To unsubscribe from this list: send the line "unsubscribe linux-raid" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html