Dark data is the huge chunk of company info—often 55% or more—that sits unused...

https://zaneznae304.lucialpiazzale.com/why-keeping-dark-data-on-flash-wastes-your-storage-budget

Dark data is the huge chunk of company info—often 55% or more—that sits unused and forgotten. It wastes up to $2.5 million yearly on storage and adds risk by cluttering security checks