Kernel: 2.6.21.1
Here is the bug:
md2: RAID1 (works fine)
md3: RAID5 (only syncs at the sync_speed_min set by the kernel)
If I do not run this command:
echo 55000 > /sys/block/md3/md/sync_speed_min
I will get 2 megabytes per second check speed for RAID 5.
However, the odd part is I can leave it the default for RAID1 and it will
use the maximum IO available between both drives to run the check.
I think there is some kind of bug, essentially with RAID5 check's-- it
only runs at the minimum value set (default in the kernel for raid5 is
~2mb/s).
md2 : active raid1 sdb3[1] sda3[0]
55681216 blocks [2/2] [UU]
[===========>.........] check = 59.1% (32937536/55681216)
finish=7.4min speed=50947K/sec
md3 : active raid5 sdl1[9] sdk1[8] sdj1[7] sdi1[6] sdh1[5] sdg1[4] sdf1[3]
sde1[
2] sdd1[1] sdc1[0]
1318686336 blocks level 5, 128k chunk, algorithm 2 [10/10]
[UUUUUUUUUU]
[====>................] check = 24.2% (35578816/146520704)
finish=33.3min speed=55464K/sec
Set to default kernel settings, either 2000 or 2100:
echo 2000 > /sys/block/md3/md/sync_speed_min
Then,
md3 : active raid5 sdl1[9] sdk1[8] sdj1[7] sdi1[6] sdh1[5] sdg1[4] sdf1[3]
sde1[
2] sdd1[1] sdc1[0]
1318686336 blocks level 5, 128k chunk, algorithm 2 [10/10]
[UUUUUUUUUU]
[======>..............] check = 31.5% (46191744/146520704)
finish=715.7min speed=2335K/sec
There is some kind of nasty bug going on here with RAID 5 devices in the
kernel. Also, incase you wondered, there is little to no I/O on the RAID
5 device when this check is being run, same for the root volume.
Justin.
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