High disk I/O - jbd2/sda2-8 process

Solution 1:

I don't know if this is helpful, but we had a similar problem which turned out to caused by one of the disks in our RAID array starting to fail. This meant that every write was taking many times longer than it should have been.

We eventually found it when we rebooted and the RAID controller finally detected the issue, but we could have got an idea from checking the RAID logs.

I hope that helps (this is my first attempt at an answer here).

Solution 2:

According to the screenshots you posted, a lot of write activity is generated by the nginx worker process with PID 2202 as well as by one of the ffmpeg processes.

Do you provide some kind of media streaming or conversion service? The jdb2 process is just a symptom, not the root cause, that being the application you are providing. jbd2 is just the messenger. If the system is not used, it will show up every so often when performing a journal sync, and under heavy load, with more journal writes, you'd see it a behaviour consistent with what you described.