Re: bad performance on RAID 5

[Justin Piszcz <jpiszcz@lucidpixels.com>]

Sevrin Robstad wrote:
> I'm suffering from bad performance on my RAID5.
>
> a "echo check >/sys/block/md0/md/sync_action"
>
> gives a speed at only about 5000K/sec , and HIGH load average :
>
> # uptime
> 20:03:55 up 8 days, 19:55,  1 user,  load average: 11.70, 4.04, 1.52
>
> kernel is 2.6.18.1.2257.fc5
> mdadm is v2.5.5
>
> the system consist of an athlon XP1,2GHz and two Sil3114 4port S-ATA 
> PCI cards with a total of 6  250gb S-ATA drives connected.
>
> [root@compaq ~]# mdadm --detail /dev/md0
> /dev/md0:
>        Version : 00.90.03
>  Creation Time : Tue Dec  5 00:33:01 2006
>     Raid Level : raid5
>     Array Size : 1218931200 (1162.46 GiB 1248.19 GB)
>    Device Size : 243786240 (232.49 GiB 249.64 GB)
>   Raid Devices : 6
>  Total Devices : 6
> Preferred Minor : 0
>    Persistence : Superblock is persistent
>
>    Update Time : Wed Jan 17 23:14:39 2007
>          State : clean
> Active Devices : 6
> Working Devices : 6
> Failed Devices : 0
>  Spare Devices : 0
>
>         Layout : left-symmetric
>     Chunk Size : 256K
>
>           UUID : 27dce477:6f45d11b:77377d08:732fa0e6
>         Events : 0.58
>
>    Number   Major   Minor   RaidDevice State
>       0       8        1        0      active sync   /dev/sda1
>       1       8       17        1      active sync   /dev/sdb1
>       2       8       33        2      active sync   /dev/sdc1
>       3       8       49        3      active sync   /dev/sdd1
>       4       8       65        4      active sync   /dev/sde1
>       5       8       81        5      active sync   /dev/sdf1
> [root@compaq ~]#
>
>
> Sevrin
> -
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If they are on the PCI bus, that is about right, you probably should be 
getting 10-15MB/s, but it is about right.  If you had each drive on its 
own PCI-e controller, then you would get much faster speeds.