Dark data refers to information your company collects but never uses—often...

https://mike-wiki.win/index.php/Pure_Storage_FlashBlade_and_Unstructured_Data_Growth_-_What_to_Do

Dark data refers to information your company collects but never uses—often making up 55% of stored files. This unused data takes up space, drives up storage and backup costs, and increases ransomware risk since it’s often unmonitored