Found something interesting when running iostat. Here is the output:
iostat 2
avg-cpu: %user %nice %system %iowait %steal %idle
0.78 0.00 0.75 82.98 0.00 15.49
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
sda 92.00 0.00 9822.00 0 19644
sdb 88.50 0.00 8620.00 0 17240
sdc 46.00 0.00 338.00 0 676
md0 0.00 0.00 0.00 0 0
md1 0.00 0.00 0.00 0 0
md2 0.00 0.00 0.00 0 0
avg-cpu: %user %nice %system %iowait %steal %idle
0.53 0.00 0.63 77.87 0.00 20.97
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
sda 28.50 0.00 3636.00 0 7272
sdb 31.50 0.00 4838.00 0 9676
sdc 21.50 0.00 424.00 0 848
md0 0.00 0.00 0.00 0 0
md1 0.00 0.00 0.00 0 0
md2 0.00 0.00 0.00 0 0
avg-cpu: %user %nice %system %iowait %steal %idle
0.90 0.00 1.10 79.17 0.00 18.84
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
sda 96.00 0.00 20164.00 0 40328
sdb 91.50 0.00 18014.00 0 36028
sdc 49.00 0.00 7512.00 0 15024
md0 0.00 0.00 0.00 0 0
md1 0.00 0.00 0.00 0 0
md2 0.00 0.00 0.00 0 0
cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4]
[raid10]
md2 : active raid5 sda6[2] sdc6[0] sdb6[1]
1757813760 blocks super 1.2 level 5, 512k chunk, algorithm 2 [3/3] [UUU]
md1 : active raid1 sda5[2] sdb5[1] sdc5[0]
78318520 blocks super 1.2 [3/3] [UUU]
md0 : active raid1 sdc1[0] sda1[2] sdb1[1]
19529656 blocks super 1.2 [3/3] [UUU]
I checked /proc/diskstats and only the sd*5 partition is being written to.
Correct me if I'm wrong but this must mean something is writing to all 3 disks
to the sd*5 partitions, but is not going through the md1 device.
This process correlates perfectly with the problems I have been having.
I have just watched over the last 2 hours that every time the server
becomes io-bound it is because of this process writing to the disks.
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https://bugs.launchpad.net/bugs/815540
Title:
Server becomes unresponsive after spawning 16 ksoftirqd processes
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