Reservation: preallocating space to a file

VxFS makes it possible to preallocate space to a file at the time of the request rather than when data is written into the file. This space cannot be allocated to other files in the file system. VxFS prevents any unexpected out-of-space condition on the file system by ensuring that a file's required space will be associated with the file before it is required.

A persistent reservation is not released when a file is truncated. The reservation must be cleared or the file must be removed to free the reserved space.