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 > >> > >> > >> > > > > > > > > > - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
