Caching is the process by which frequently accessed or newly written data is fetched from or written to a small and faster memory, called a cache.

Dirty memory is data-backed (for example, file-backed) memory whose content has been modified (typically in a cache) but not written back to the disk yet. The cached version of the data is newer than the on-disk version, meaning that both versions are out of sync. The mechanism by which cached data is written back on the disk (back store) is called writeback. We will eventually update the on-disk version, bringing the two in sync. Clean memory is file-backed memory in which the contents are in sync with the disk.

Linux delays write operations in order to speed up the read process, and reduces disk wear leveling by writing data only when necessary. A typical example is the dd command. Its complete execution does...