monitor I/O with iotop

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monitor I/O with iotop

sysadmin

iotop is a nice tool to monitor I/O usage information output by the Linux kernel (requires 2.6.20 or later).

To install iotop with yum as root (for RedHat / Fedora / Centos based systems only)


[root@blackmod ~]# yum install iotop

Start iotop with the "-d .5" option (refreshes every 0.5 seconds):


[root@blackmod ~]# iotop -d .5

Because we are not doing anything at the moment it shows only 0s for all processes:

Total DISK READ: 0.00 B/s | Total DISK WRITE: 0.00 B/s TID PRIO USER DISK READ DISK WRITE SWAPIN IO> COMMAND 1 be/4 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % init 2 be/3 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [kthreadd] 3 rt/3 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [migration/0] 4 be/3 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [ksoftirqd/0] 5 rt/3 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [watchdog/0] 6 be/3 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [events/0] 7 be/3 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [cpuset] 8 be/3 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [khelper] 9 be/3 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [netns] 10 be/3 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [async/mgr] 11 be/3 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [kintegrityd/0] 12 be/3 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [kblockd/0] 13 be/3 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [kacpid] 14 be/3 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [kacpi_notify] 15 be/3 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [kacpi_hotplug] 16 be/3 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [ata/0] 17 be/3 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [ata_aux] 18 be/3 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [ksuspend_usbd] 19 be/3 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [khubd] 20 be/3 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [kseriod] 21 be/4 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [khungtaskd] 22 be/4 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [pdflush] 23 be/4 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [pdflush] 24 be/3 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [kswapd0] 25 be/5 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [ksmd] 26 be/3 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [aio/0] 27 be/3 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [crypto/0] 33 be/3 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [scsi_eh_0] 34 be/3 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [scsi_eh_1] 1059 be/4 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % acpid 36 be/3 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [kpsmoused] 37 be/3 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [kstriped] 38 be/3 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [ksnapd] 39 be/3 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [usbhid_resumer]

Now, open a second terminal and generate some I/O with "dd" (make sure you have at least 500MB left in your /tmp filesystem):

 
[mod@blackmod ~]$ dd if=/dev/zero of=/tmp/dump bs=1M count=500

Go back to the iotop session and see how it looks now:

Total DISK READ: 0.00 B/s | Total DISK WRITE: 33.97 M/s TID PRIO USER DISK READ DISK WRITE SWAPIN IO> COMMAND 332 be/3 root 0.00 B/s 0.00 B/s 0.00 % 93.10 % [kjournald2] 2631 be/4 mod 0.00 B/s 30.02 M/s 0.00 % 85.55 % dd if=/dev/zero of=/tmp/dump bs=1M count=500 22 be/4 root 0.00 B/s 120.07 K/s 0.00 % 82.64 % [pdflush] 2531 be/4 root 0.00 B/s 210.13 K/s 0.00 % 81.23 % [pdflush] 248 be/3 root 0.00 B/s 0.00 B/s 0.00 % 31.83 % [kdmflush] 731 be/3 root 0.00 B/s 0.00 B/s 0.00 % 1.81 % [kjournald2] 2506 be/4 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % packagekitd 1 be/4 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % init 2 be/3 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [kthreadd] 3 rt/3 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [migration/0] 4 be/3 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [ksoftirqd/0] 5 rt/3 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [watchdog/0] 6 be/3 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [events/0] 7 be/3 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [cpuset] 8 be/3 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [khelper] 9 be/3 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [netns] 10 be/3 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [async/mgr] 11 be/3 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [kintegrityd/0] 12 be/3 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [kblockd/0] 13 be/3 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [kacpid] 14 be/3 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [kacpi_notify] 15 be/3 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [kacpi_hotplug] 16 be/3 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [ata/0] 17 be/3 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [ata_aux] 18 be/3 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [ksuspend_usbd] 19 be/3 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [khubd] 20 be/3 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [kseriod] 21 be/4 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [khungtaskd] 24 be/3 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [kswapd0] 25 be/5 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [ksmd] 26 be/3 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [aio/0] 27 be/3 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [crypto/0] 33 be/3 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [scsi_eh_0] 34 be/3 root 0.00 B/s 0.00 B/s 0.00 % 0.00 % [scsi_eh_1]