VxFS allocates disk space to files in groups of one or more extents. VxFS also allows applications to control some aspects of the extent allocation. Extent attributes are the extent allocation policies associated with a file.

The setext and getext commands allow the administrator to set or view extent attributes associated with a file, as well as to preallocate space for a file.

Because these facilities are provided using VxFS-specific IOCTL system calls, most existing UNIX system applications do not use them. The cp, cpio, and mv utilities use the facilities to preserve extent attributes and allocate space more efficiently. The current attributes of a file can be listed using the getext command. The facilities can also improve performance for custom applications. For portability reasons, these applications must check which file system type they are using before using these interfaces.

See the setext(1) and getext(1) manual pages.