Dstat Logging

To log the data in a csv format so that it can be used later for processing & generate graphs

dstat -ts --top-io --top-bio --noheaders --nocolor --output /tmp/dstat.csv 5 > /dev/null &

The main output is redirected to /dev/null, which means it won't get 
written anywhere.  Instead you'll get a CSV file at /tmp/dstat.csv.

Schedule it via cron every minute

#  Run dstat and log the reports

* * * * * root dstat -ts --top-io --top-bio --noheaders --nocolor 5 3 >> /var/log/dstat.txt

If you prefer a log of the data in CSV format, put this into the file instead:

#  Run dstat and log the reports

* * * * * root dstat -ts --top-io --top-bio --noheaders --nocolor --output /var/log/dstat.csv 5 3 > /dev/null

Rotate the created log



If you plan to leave the dstat logger running (and aren't just going 
to run it for a day or so to check on a burst of disk activity) you'll 
want to rotate its log occasionally to keep it from getting too big.

To that end, create a file for editing at "/etc/logrotate.d/dstat" and put the below entry to this.

/var/log/dstat.csv {
  rotate 5
  weekly
  compress
  missingok
  notifempty
}

Also

use "iotop" & "vmstat 1" 

run vmstat 1 and watch the bo (buffer out) column.

If it's a userspace process you may see it with "iotop".