Dark data is the inactive information companies store but rarely use—about...

https://romeo-wiki.win/index.php/How_Do_I_Deal_with_Old_Media_Assets_and_Temp_Files_at_Scale%3F

Dark data is the inactive information companies store but rarely use—about 60-80% of all data. It quietly takes up space and costs money, with some businesses wasting up to $2.5 million a year just maintaining it