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Veritas File System (VxFS) provides API functions frequently associated with commercial applications that make it possible to perform the following actions:
Preallocate space for a file
Specify a fixed extent size for a file
Bypass the system buffer cache for file I/O
Specify the expected access pattern for a file
Because these functions are provided using VxFS-specific IOCTL system calls, most existing UNIX system applications do not use them. The VxFS-specific cp, cpio, and mv utilities use the functions to preserve extent attributes and allocate space more efficiently. The current attributes of a file can be listed using the getext or VxFS-specific ls command. The functions can also improve performance for custom applications. For portability reasons, these applications must check which file system type they are using before using these functions.
See the cp_vxfs(1), cpio_vxfs(1), and mv_vxfs(1) manual pages.