Veritas File System 5.1 SP1 Administrator"s Guide (5900-1499, April 2011)

Write operations beyond reservation

A reservation request can specify that no allocations can take place after a write

operation fills the last available block in the reservation. This request can be used

a way similar to the function of the ulimit command to prevent a file's

uncontrolled growth.

Reservation trimming

A reservation request can specify that any unused reservation be released when

the file is closed. The file is not completely closed until all processes open against

the file have closed it.

Reservation persistence

A reservation request can ensure that the reservation does not become a persistent

attribute of the file. The unused reservation is discarded when the file is closed.

Including reservation in the file

A reservation request can make sure the size of the file is adjusted to include the

reservation. Normally, the space of the reservation is not included in the file until

an extending write operation requires it. A reservation that immediately changes

the file size can generate large temporary files. Unlike a ftruncate operation that

increases the size of a file, this type of reservation does not perform zeroing of

the blocks included in the file and limits this facility to users with appropriate

privileges. The data that appears in the file may have been previously contained

in another file. For users who do not have the appropriate privileges, there is a

variant request that prevents such users from viewing uninitialized data.

Commands related to extent attributes

The VxFS commands for manipulating extent attributes are setext and getext;

they allow the user to set up files with a given set of extent attributes or view any

attributes that are already associated with a file.

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

The VxFS-specific commands vxdump and vxrestore preserve extent attributes

when backing up, restoring, moving, or copying files.

Most of these commands include a command line option (-e) for maintaining

extent attributes on files. This option specifies dealing with a VxFS file that has

extent attribute information including reserved space, a fixed extent size, and

extent alignment. The extent attribute information may be lost if the destination

Extent attributes

Commands related to extent attributes