Dark data is the forgotten files and info sitting unused on your servers....

https://dantevrib041.fotosdefrases.com/what-should-i-track-monthly-to-prevent-dark-data-from-creeping-back

Dark data is the forgotten files and info sitting unused on your servers. Around 55% of enterprise data goes dark, costing companies up to $2.5 million a year in wasted storage and management