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#1 2012-03-27 17:57:12

Registered: 2011-10-05
Posts: 7

High IO wait caused by jbd2


I have some problems with my little home server. Sometimes it's performance is very bad and even commands through ssh are extremely laggy and the IO performance is very bad. I have to say this problem only occurs sometimes, about 30 - 50 % of the time. Sometimes everything is ok after a reboot and a few hours later the problem is back. I am using two Western Digital "Caviar Black" HDDs in a software RAID1 with mdadm, it seems to be fine:

$ cat /proc/mdstat 
Personalities : [raid1] 
md3 : active raid1 sda4[0] sdb4[1]
      467282560 blocks [2/2] [UU]
md2 : active raid1 sda3[0] sdb3[1]
      16787840 blocks [2/2] [UU]
md1 : active raid1 sda2[0] sdb2[1]
      4200896 blocks [2/2] [UU]
md0 : active raid1 sda1[0] sdb1[1]
      112320 blocks [2/2] [UU]
unused devices: <none>

top reports high IO wait times:

Cpu(s):  2.9%us,  8.4%sy,  7.2%ni, 45.0%id, 36.5%wa,  0.0%hi,  0.0%si,  0.0%st

iotop says this is caused by jbd2:

109 be/3 root        0.00 B/s    0.00 B/s  0.00 % 99.99 % [jbd2/md2-8]

The strangest thing is that this problem occurs not everytime. Sometimes I have this problem a few days, sometimes everything is running fine for days. I also looked at the S.M.A.R.T values but also everything looks fine and no bad sectors are reported.

My /etc/fstab looks like this:

tmpfs           /tmp    tmpfs   nodev,nosuid,size=4G    0       0
/dev/md0 /boot ext2 defaults 0 1
/dev/md1 swap swap defaults 0 0
/dev/md2 / ext4 defaults 0 1
/dev/md3 /home ext4 defaults 0 1

Sometimes this problem stays for hour or days, sometimes it's gone after half a hour. dmesg seems to look fine also..

I don't know, please help me. I never had similar problems before and I have no idea where I have to look or what I should try to fix this issue.

Thank you very much...


#2 2012-03-28 04:05:13

Registered: 2010-04-27
Posts: 1,237

Re: High IO wait caused by jbd2

Something is syncing to disk too often (logs, bitcoin, ...). … ds-788810/

Steven [ web : git ]
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#3 2012-03-28 19:09:14

Forum Fellow
From: Between a computer and a chair
Registered: 2008-09-14
Posts: 4,734

Re: High IO wait caused by jbd2

Do you have any program regularly indexing disk contents? Those usually can slow the system to a halt.



#4 2014-09-14 00:51:51

Registered: 2014-09-14
Posts: 5

Re: High IO wait caused by jbd2

I know this is an old topic, but this solved the issue for me: … io-problem


#5 2014-09-14 01:09:49

From: Pasadena, CA
Registered: 2009-07-13
Posts: 19,691

Re: High IO wait caused by jbd2

I am glad that solved it for you, and it is relevant to an old thread, so posting is fine.
Also, welcome to Arch Linux.

Regardless, I am going to go ahead and close this old thread

Nothing is too wonderful to be true, if it be consistent with the laws of nature -- Michael Faraday
Sometimes it is the people no one can imagine anything of who do the things no one can imagine. -- Alan Turing
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