Disk usage related information

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If the performance of a system is poor, then the most common reasons for poor performance are high usage of CPU, memory, network or disk. CPU usage can be monitored using top or htop, memory usage can be seen using free -m or top, network usage can be seen using iptraf, tcptrack, etc. Similalry for disk usage one can use:

1. iostat
2. iotop
3. atop

iostat

One can use following command:

iostat 5

to see disk usage in last five seconds to see if disk usage is very high. The first set of values printed are cumulative till the command was run, so they should be ignored. Second set of values onwards can be used for actual diagnosis.

iotop

Sometimes machine may be too slow and using top may indicate very high value of %wa indicating slowness due to disk I/O. If this continues for long even load average would increase to indicate slow performance. To figure out which processes are using more disk we can install 'iotop' tool which lists processes in order of their disk usage.

To see top like listing of processes but in terms of their disk usage and not CPU, one can use:

iotop

atop

Information on atop is available at Rocky 9.x atop

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