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

https://lukasnpyy234.cavandoragh.org/how-do-i-make-nas-and-object-storage-searchable-like-google

Dark data is the inactive or unused information that piles up in your storage—often making up 55% of all enterprise data. This unused data increases costs through wasted storage and backups, and it raises your risk of breach or ransomware exposure