CentOS6 and long Wait IO time on jbd2/dm-0-8
Linux box running CentOS 6.5 and 2.6.32-431.3.1.el6.i686 kernel recently got CPU spikes up to 99% causing by Wait IO.
Executing
while true; do date; ps auxf | awk '{if($8=="D") print $0;}'; sleep 1; done
gives me on those CPU spikes:
root 300 0.0 0.0 0 0 ? D 10:05 0:00 \_ [jbd2/dm-0-8]
so it let me think that source of those spikes is Journal Disk.
I found that topic to be similar IO Wait causing so much slowdown (EXT4 JDB2 at 99% IO ) During Mysql Commit but I have no clue where I can find if my partitions are journaling data or not. My fstab looks like
/dev/mapper/vg_ns01-lv_root / ext4 defaults 1 1
UUID=bc042a99-90a1-4d0a-a7b6-4122e9b2a201 /boot ext4 defaults 1 2
/dev/mapper/vg_ns01-lv_home /home ext4 defaults 1 2
/dev/mapper/vg_ns01-lv_swap swap swap defaults 0 0
tmpfs /dev/shm tmpfs defaults 0 0
devpts /dev/pts devpts gid=5,mode=620 0 0
sysfs /sys sysfs defaults 0 0
proc /proc proc defaults 0 0
Thanks
To check if a partition has journal enabled:
tune2fs -l /dev/mapper/vg_ns01-lv_root | grep has_journal
Due I'm not able to disable journal on my root partition I have added
noatime,nodiratime,barrier=1,data=ordered
to the fstab and enabled wrtieback on journal and enabled data writeback on journal
tune2fs -o journal_data_writeback /dev/mapper/vg_ns01-lv_root
In result, so far, I'm not getting long Wait IO on that partition.