How to Monitor Disk IO in a Linux System

Abstract

Disk monitoring is an important task to perform while maintaining a linux system. Essentially, getting data back from the disk costs time. As a result, the disk I/O subsystem is considered the slowest part and can slow down the whole system.

Checking disc performance is crucial as a result. We must determine which process is waiting for the I/O request to complete and determine whether there is a bottleneck and what is causing it. To examine the disc I/O performance in Linux systems, we'll learn how to use tools like iostat, iotop..

iotop installation in Linux

It is readily simple to install with the aid of a package manager because the package is present in the repositories of all Linux distributions.

Iotop can be installed using the DNF Command on Fedora and RHEL/CentOS 8 systems.

$ sudo dnf install iotop

Iotop can be installed on Debian/Ubuntu systems using the APT-GET Command or the APT Command.

$ sudo apt install iotop

Iotop can be installed on RHEL/CentOS 6/7 systems using the YUM Command

$ sudo yum  install iotop

Using the iotop command to monitor disc I/O

The iotop command offers a wide range of options for checking various disc I/O statistics.

To view the current I/O utilization for each process or thread, run the iotop command without any parameters.

$ sudo iotop

Output

 Total DISK READ :      18.27 K/s   |  Total DISK WRITE :       0.00 B/s
 0.00 B DISK READ:      18.27 K/s  |  Actual DISK WRITE:      14.61 K/s
     TID  PRIO  USER    DISK READ   DISK WRITE   SWAPIN     IO>        COMMAND                                                                                                
      509 be/3 root         0.00 B/s    0.00 B/s           0.00 %     3.91 %    [jbd2/dm-0-8]
      247269 be/4           0.00 B/s    0.00 B/s           0.00 %     0.21 %    kworker/0:2]
      2507 be/4 nwd         18.2 B/s    0.00 B/s           3.57 %     0.00 %    gnome-terminal
      1 be/4 root           0.00 B/s    0.00 B/s           0.00 %     0.00 %    systemd --switch
      2 be/4 root           0.00 B/s    0.00 B/s           0.00 %     0.00 %    [kthreadd]
      3 be/0 root           0.00 B/s    0.00 B/s           0.00 %     0.00 %    [rcu_gp]
      4 be/0 root           0.00 B/s    0.00 B/s           0.00 %     0.00 %    [rcu_par_gp]
      6 be/0 root           0.00 B/s    0.00 B/s           0.00 %     0.00 %    [kworker/0]
      9 be/0 root           0.00 B/s    0.00 B/s           0.00 %     0.00 %    [mm_percpu_wq]
     10 be/4 root           0.00 B/s    0.00 B/s           0.00 %     0.00 %    [rcu_tasks_kthre]
     11 be/4 root           0.00 B/s    0.00 B/s           0.00 %     0.00 %    [rcu_tasks_rude_]
     12 be/4 root           0.00 B/s    0.00 B/s           0.00 %     0.00 %    [rcu_tasks_trace]
     13 be/4 root           0.00 B/s    0.00 B/s           0.00 %     0.00 %    [ksoftirqd/0]
     14 be/4 root           0.00 B/s    0.00 B/s           0.00 %     0.00 %    [rcu_sched]

iostat installation in Linux

Iostat can be installed using the DNF Command on Fedora and RHEL/CentOS 8 systems.

$ sudo dnf install sysstat

Iostat can be installed on Debian/Ubuntu systems using the APT-GET Command or the APT Command.

$ sudo apt install sysstat

Iostat can be installed on RHEL/CentOS 6/7 systems using the YUM Command

$ sudo yum  install sysstat

Using the iostat command to monitor disc I/O

The iostat command offers a wide range of options for checking various CPU and disc I/O statistics.

To view the whole system statistics, run the iostat command without any arguments.

$ iostat

Output

Linux 4.19.32-1-MANJARO  	Thursday 18 April 2022 	_x86_64_	(8 CPU)

avg-cpu:  %user   %nice  %system  %iowait   %steal   %idle
                  29.45    0.02    16.47        0.12          0.00     53.94

Device             tps     kB_read/s    kB_wrtn/s    kB_dscd/s    kB_read     kB_wrtn    kB_dscd
nvme0n1           6.68       126.95        124.97       0.00      58420014   57507206          0
sda               0.18         6.77         80.24       0.00      3115036    36924764          0
loop0             0.00         0.00         0.00        0.00      2160              0          0
loop1             0.00         0.00         0.00        0.00      1093              0          0
loop2             0.00         0.00         0.00        0.00      1077              0          0
sda               3.14        63.31         38.14       0.00      19772796    11911070         0
scd0              0.00         0.00         0.00        0.00      1                 0          0
zram0             7.74         9.36         21.58       0.00      2924188     6738944          0

Conclusion

In this article, we learnt how to examine disc I/O performance using the iostat and iotop. We also talked about using the iotop command to view disc read and write activity broken down by process.

There are several other commands i.e., vmstat and sar commands which can be used to monitor disk in I/O in a Linux system. I hope you find these examples of the commands useful and that it's easy to learn and use Linux.