Re: bad performance on RAID 5

[Sevrin Robstad <quackyo@start.no>]

Justin Piszcz 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.
>
>

There are two controllers, 4 disks connected to one controller on the 
PCI-bus and 2 disks connected to the other controller.
As you say I should have had 10-15MB/s, but I'm having 5MB *and* with 
really high load average.

Sevrin