Dark data is the inactive or unused info lurking in your systems — often 60% to...

https://shed-wiki.win/index.php/How_Does_Dark_Data_Build_Up_After_Backups_and_Replication%3F

Dark data is the inactive or unused info lurking in your systems — often 60% to 80% of it. It’s not just wasting storage and money but also creating risk and clutter that can confuse AI projects