HP JFS 3.3 and HP OnLineJFS 3.3 VERITAS File System 3.3 System Administrator's Guide

74 Chapter3
Extent Attributes
Introduction
Introduction
The VxFS file system allocates disk space to files in groups of one or more
adjacent blocks called extents . VxFS defines an application interface
that allows programs to control various aspects of the extent allocation
for a given file (see Chapter 6 , “Application Interface”). The extent
allocation policies associated with a file are referred to as extent
attributes .
The VxFS getext and setext commands allows users to view or
manipulate file extent attributes. In addition, the vxdump, vxrestore,
mv, cp, and cpio commands preserve extent attributes when a file is
backed up, moved, copied, or archived.
NOTE setext functionality is available only with the optional HP OnLineJFS
product.
The following topics are covered in this chapter:
• “Attribute Specifics”
— “Reservation: Preallocating Space to a File”
— “Fixed Extent Size”
— “Other Controls”
• “Commands Related to Extent Attributes”
— “Failure to Preserve Extent Attributes”