The unused space on a cluster that exists when the logical file space is less than the physical file space. Also known as file slack. A form of residual data, the amount of on-disc file space from the end of the logical record information to the end of the physical disc record. Slack space can contain information soft-deleted from the record, information from prior records stored at the same physical location as current records, metadata fragments, and other information useful for forensic analysis of computer systems..”