Dark data is the unused information that piles up in your storage, often making...

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

Dark data is the unused information that piles up in your storage, often making up 55% of all data. This inactive data wastes storage and backup costs and increases risk, like ransomware exposure due to overlooked files