Extents

An extent is a contiguous area of storage in a computer file system, reserved for a file. When starting to write to a file, a whole extent is allocated. When writing to the file again, the data continues where the previous write left off. This reduces or eliminates file fragmentation.

Since VxFS is an extent-based file system, addressing is done through extents (which can consist of multiple blocks) rather than in single-block segments. Extents can therefore enhance file system throughput.