) Steve Cousins wrote:
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 :
What do you get when you try something like:
time dd if=/dev/zero of=/mount-point/test.dat bs=1024k count=1024
That doesn't give valid (repeatable) results due to caching issues. Go
back to the thread I started on RAID-5 write, and see my results. More
important, the way I got rid of the cache effects (beside an unloaded
systems) was:
sync; time bash -c "dd if=/dev/zero bs=1024k count=2048
of=/mnt/point/file; sync"
I empty the cache, then time the dd including the sync at the end.
Results are far more repeatable.
I actually was able to create custom arrays on unused devices to play
with array setting, once you use the array you can't tune as much.
where /mount-point is where /dev/md0 is mounted.
This will create a 1 GiB file and it will tell you how long it takes
to create it. Also, I'd try running Bonnie++ on it to see what the
different performance values are.
I don't know a lot about the md sync process but I remember having my
sync action stuck at a low value at one point and it didn't have
anything to do with the performance of the RAID array in general.
Steve
# 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
--
bill davidsen <davidsen@xxxxxxx>
CTO TMR Associates, Inc
Doing interesting things with small computers since 1979
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