Veritas File System 4.1 Administrator's Guide (HP-UX 11i v3, February 2007)

Extent Attributes
Attribute Specifics
Chapter 354
Attribute Specifics
The two basic extent attributes associated with a file are its reservation and its fixed extent size. You can
preallocate space to the file by manipulating a file’s reservation, or override the default allocation policy of
the file system by setting a fixed extent size.
Other policies determine the way these attributes are expressed during the allocation process. You can
specify that:
• The space reserved for a file must be contiguous
• No allocations are made for a file beyond the current reservation
• An unused reservation is released when the file is closed
• Space is allocated, but no reservation is assigned
• The file size is changed to immediately incorporate the allocated space
Some of the extent attributes are persistent and become part of the on-disk information about the file, while
other attributes are temporary and are lost after the file is closed or the system is rebooted. The persistent
attributes are similar to the file’s permissions and are written in the inode for the file. When a file is copied,
moved, or archived, only the persistent attributes of the source file are preserved in the new file (see “Other
Controls” on page 56 for more information).
In general, the user will only set extent attributes for reservation. Many of the attributes are designed for
applications that are tuned to a particular pattern of I/O or disk alignment (see the mkfs_vxfs (1M) manual
page and “Application Interface” on page 59 for more information).