What is slack space on a disk?

Slack space on a disk is defined as the area between the end-of-file marker and the end of the cluster that holds the file. When files are saved to a disk, they are allocated in clusters, which are fixed-size blocks of disk space. If the file doesn't completely fill the last cluster allocated for it, the remaining space within that cluster is considered slack space. This space can sometimes contain remnants of previously deleted files or other data that could be recovered, making it significant in digital forensics and data recovery contexts.

The other options describe different concepts. Unused space in a data center typically refers to physical space not currently occupied by hardware or data but does not relate specifically to disk structure. Data that is replicated for recovery pertains to redundancy and backup strategies, while space reserved for system processes relates to operational requirements of the system rather than the specific term 'slack space.'