Sign up ×
Server Fault is a question and answer site for system and network administrators. It's 100% free, no registration required.

I have a server with Debian 6 and software RAID1. There is a problem: every few seconds the jbd2/md2-8 process loads all the HDD IO. It was detected by iotop. And for the md2_raid1 process 99% of IO displays.

The flush-9:2 process every few seconds loads 99% of CPU in top.

What can I do to optimize this system? Can transition to hardware RAID help in this situation?

This is cat /proc/mdstat

Personalities : [raid0] [raid1] [raid6] [raid5] [raid4] [raid10]
md3 : active raid1 sda4[0] sdb4[1]
      1822442815 blocks super 1.2 [2/2] [UU]

md2 : active raid1 sda3[0] sdb3[1]
      1073740664 blocks super 1.2 [2/2] [UU]

md1 : active raid1 sda2[0] sdb2[1]
      524276 blocks super 1.2 [2/2] [UU]

md0 : active raid1 sda1[0] sdb1[1]
      33553336 blocks super 1.2 [2/2] [UU]

unused devices: <none>
share|improve this question

migrated from May 22 '12 at 12:59

This question came from our site for professional and enthusiast programmers.

Yes, transitioning to hardware RAID would help the situation. –  Petesh May 11 '12 at 7:58
have the same problem, my disks seem to be ok, I checked them with smartctl. It is really strange because the box becomes unresponsive –  Janning Jun 12 '12 at 14:55

2 Answers 2

next time this happens, run the following command "cat /proc/mdstat" then paste the output here

share|improve this answer
I have pasted it in main text –  Andre-487 May 13 '12 at 17:07
Hello, sorry that I had never responded, was looking around just now, and it seems that something called noflushd can cause issues like what you are describing. Check out this article to see what I am talking about… –  lacrosse1991 Feb 2 '13 at 20:18

Your software raid is taking all the CPU cycles in order to run the RAID. Getting a hardware RAID can help. Keep in mind that if you want to take full advantage of a RAID controller you will need to ensure it has a BBU (battery back up) in order to enable the cache and write-back mode.

Depending on what is important to you, you could turn on RAID 0 (striping) and get even better performance out of your system, but even a regular RAID hardware controller will help.

share|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.