Dark data is the vast amount of information companies store but never use—up to...

https://fair-wiki.win/index.php/Why_Do_Backup_Costs_Explode_When_You_Keep_Old_Files%3F

Dark data is the vast amount of information companies store but never use—up to 80% can sit inactive. It matters because this unused data costs businesses around $2.5 million every year in storage and management