Monitoring 101: Collecting the right data - Datadog
www.datadoghq.com/blog/monitoring-101-collecting-data
From the page
Saved with the link. Notes from 2007 to 2016 are mostly the page's own words, so this is probably an excerpt.
Collect and classify data so that you can receive meaningful, automated alerts about potential problems, and quickly get to the bottom of performance issues