PostgreSQL 12 High Availability Cookbook - Third Edition

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While the iotop data is not actually part of the statistics gathered automatically by the sysstat package, we can log the data for posterity anyway. Follow these steps as a root-level user to log the iostat data:

1. Create a file named iotop at /etc/cron.d/ and fill it with this line:

* * * * * root iotop -boat -qqq -d 5 -n 2 >> /var/log/iotop 

2. Reload the configuration files of the cron service with this command:

sudo systemctl restart cron

3. If the previous command didn't work, try this:

sudo systemctl restart crond

By adding the -a parameter, iotop will log the cumulative total of the I/O used between the readings instead of the I/O per second. We use the -d argument to add a 5-second delay between two readings, as specified ...