If your Linux system gets slow down due to heavy disk I/O activities, you probably want to know which processes or users (in case of multi-user systems) are the culprit for such activities. You may also wish to monitor disk I/O trending over time as part of daily Linux system administration. Here I will introduce several disk I/O monitoring tools on Linux.
Monitor disk I/O on per-process basis
If you want to monitor disk I/O activities of individual Linux processes, you can try iotop. This tool shows a sorted list of the most I/O intensive processes in real time via top-like interface.
To install iotop on Ubuntu or Debian, run the following.
To install iotop on Fedora, run:
To install iotop on CentOS or RHEL, first set up RepoForge repository on your system, and then use yum command.
To monitor disk I/O with iotop:
Running iotop without any argument like above shows a list of all existing processes regardless of their disk I/O activities. If you want iotop to only show processes that are actually doing disk I/O, run the following instead.
Monitor disk I/O on per-disk basis
If you are interested in monitoring disk read/write rates of individual disks, you can use iostat. This tool allows you to monitor I/O statistics for each device or partition. To use this tool, you need to run sysstat package.
To install sysstat on Ubuntu or Debian:
To install sysstat on CentOS, RHEL or Fedora:
To monitor disk I/O of individual disk devices:
The above iostat command will report per-device I/O statistics, including # of read/write requests per second (noted as r/s, w/s), average read/write speed (in KB/s), average read/write wait time (in milliseconds), average size of requests (in sectors), and percentage of CPU time spent for I/O requests. The statistics are refreshed every time interval specified.
To monitor disk I/O of individual disk partitions:
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