Dark data is the inactive or unused information that piles up in your...

https://highstylife.com/why-do-rag-pipelines-get-worse-when-you-add-more-documents/

Dark data is the inactive or unused information that piles up in your storage—often 55% of all stored data. It wastes money on storage and backup costs and increases risks like ransomware exposure since old files are less likely to be secured