02. [30p] iostat & iotop

[15p] Task A - Monitoring the behaviour with Iostat

Parameteres for iostat:

  • -x for extended statistics
  • -d to display device stastistics only
  • -m for displaying r/w in MB/s
$ iostat -xdm

Use iostat with -p for specific device statistics:

$ iostat -xdm -p sda

  • Run iostat -x 1 5.
  • Considering the last two outputs provided by the previous command, calculate the efficiency of IOPS for each of them. Does the amount of data written per I/O increase or decrease?

Add in your archive screenshot or pictures of the operations and the result you obtained, also showing the output of iostat from which you took the values.

How to do:

  • Divide the kilobytes read (rkB/s) and written (wkB/s) per second by the reads per second (r/s) and the writes per second (w/s).
  • If you happen to have quite a few loop devices in your iostat output, find out what they are exactly:
$ df -kh /dev/loop*

[15p] Task B - Monitoring the behaviour with Iotop

Iotop is an utility similar to top command, that interfaces with the kernel to provide per-thread/process I/O usage statistics.

Debian/Ubuntu Linux install iotop
$ sudo apt-get install iotop

How to use iotop command
$ sudo iotop OR $ iotop

Supported options by iotop command:

Options Description
–version show program’s version number and exit
-h, –help show this help message and exit
-o, –only only show processes or threads actually doing I/O
-b, –batch non-interactive mode
-n NUM, –iter=NUM number of iterations before ending [infinite]
-d SEC, –delay=SEC delay between iterations [1 second]
-p PID, –pid=PID processes/threads to monitor [all]
-u USER, –user=USER users to monitor [all]
-P, –processes only show processes, not all threads
-a, –accumulated show accumulated I/O instead of bandwidth
-k, –kilobytes use kilobytes instead of a human friendly unit
-t, –time add a timestamp on each line (implies –batch)
-q, –quiet suppress some lines of header (implies –batch)

  • Run iotop (install it if you do not already have it) in a separate shell showing only processes or threads actually doing I/O.
  • Inspect the script code (dummy.sh) to see what it does.
  • Monitor the behaviour of the system with iotop while running the script.
  • Identify the PID and PPID of the process running the dummy script and kill the process using command line from another shell (sending SIGINT signal to both parent & child processes).

Provide a screenshot in which it shows the iotop with only the active processes and one of them being the running script. Then another screenshot after you succeeded to kill it.

ep/labs/03/contents/tasks/ex2.txt · Last modified: 2022/09/13 12:59 by radu.mantu
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