Dark data is the inactive or unseen information companies keep but don’t use....

https://wiki-site.win/index.php/Why_Do_RAG_Pipelines_Get_Worse_When_You_Add_More_Documents%3F

Dark data is the inactive or unseen information companies keep but don’t use. It can be up to 60-80% of stored data, leading to wasted storage and backup costs that can reach millions annually