Veritas File System (VxFS) allows the user to set the fixed extent size option on a file that controls the minimum allocation size of the file. If a file has shared extents that must be unshared, the allocation that is done as a part of the unshare operation ignores the fixed extent size option that is set on the file. The allocation size during the unshare operation, is dependent on the size of the write operation on the shared region.