VERITAS File System 4.1 Administrator's Guide

Extent Attributes
Attribute Specifics
Chapter 370
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 72 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 75 for more information).