 The file system "could" defragment the disk immediately after a deletion, but doing so would incur a severe performance penalty at unpredictable times.Now, a new file called F, which requires seven blocks of space, can be placed into the first seven blocks of the newly freed space formerly holding the file B, and the three blocks following it will remain available.If another new file called G, which needs only three blocks, is added, it could then occupy the space after F and before C.

If subsequently F needs to be expanded, since the space immediately following it is occupied, there are three options for the file system