How do I tell which processes are writing heavily to disk in CentOS 5?

hard-drive io iostat

10,241

Solution 1

So sadly none of the iostat and related packages work in CentOS 5. But I was able to find the culprit slow process by using:

ps auxf | grep ' B'

Which shows all the processes waiting in uniterruptible sleep caused by I/O waiting, so it is likely to be processes doing a lot of I/O.

This was thanks to this ServerFault answer: wa (Waiting for I/O) from top command is big

Also, for those wondering if the I/O is slow because of swapping, take a look at your top output and see what the sum of (free + cached) columns says. Or better use htop, which shows this in a less confusing way.

Solution 2

I also like iotop

Solution 3

collectl may be what you are after. I/O statistics by process, among other things. collectl --top io to print a top-like listing sorted by IO usage, collectl -sZ for collectl native output for the processes subsystem. Adding the --procopts t switch will show threads too.

As Richard Salts mentioned, IOTop will give you a UI with more detailed I/O stats, if you have a window manager and Python then use that. In either case though, if your kernel doesn't support it (2.6.20 or later is a safe bet) then neither program will work.

10,241

Author by

Artem

Updated on September 17, 2022

Comments

Artem almost 2 years
Our server started getting slow, so I ran iostat on it.

iostat -dx 5
```
Device:         rrqm/s   wrqm/s   r/s   w/s   rsec/s   wsec/s avgrq-sz avgqu-sz   await  svctm  %util
sda               0.00    89.60 108.40  5.60   880.00   763.20    14.41     2.61   22.87   8.70  99.20
sdb               0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00
```
So I see that the one disk sda is totally saturated. How do I find which exact processes are causing this? (or is it swapping to that disk?)
- Artem almost 14 years
  
  On CentOS 5, the kernel is the older one, and so tools like iotop do not work! See my poor man's solution to this below.
Artem almost 14 years

I am on CentOS 5.
Artem almost 14 years

As you anticipated, sadly, I get "Error: you cannot use --top and IO options with this kernel type 'collectl -h' for help" I am on CentOS 5. What are my options in this case?
vnix27 about 13 years

Its B or D. I think D state show uninterruptable sleep