Disk Scheduling is done by operating systems to schedule I/O requests for the disk. Disk Scheduling is also known as I/O Scheduling. The main goal of Disk Scheduling is to reduce the Seek Time and it is done by applying various Disk Scheduling Algorithms.

In an operating system that uses paging for memory management, a page replacement algorithm is needed to decide which page needs to be replaced when new page comes in. The process of replacement is sometimes called swap out or write to disk.