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

on the disk before the write returns, but the inode modification times may be lost
if the system crashes.
defragmentation The process of reorganizing data on disk by making file data blocks physically
adjacent to reduce access times.
direct extent An extent that is referenced directly by an inode.
direct I/O An unbuffered form of I/O that bypasses the kernel’s buffering of data. With direct
I/O, the file system transfers data directly between the disk and the user-supplied
buffer. See buffered I/O and unbuffered I/O.
discovered direct I/O Discovered Direct I/O behavior is similar to direct I/O and has the same alignment
constraints, except writes that allocate storage or extend the file size do not require
writing the inode changes before returning to the application.
encapsulation A process that converts existing partitions on a specified disk to volumes. If any
partitions contain file systems, /etc/filesystems entries are modified so that the
file systems are mounted on volumes instead. Encapsulation is not applicable on
some systems.
extent A group of contiguous file system data blocks treated as a single unit. An extent
is defined by the address of the starting block and a length.
extent attribute A policy that determines how a file allocates extents.
external quotas file A quotas file (named quotas) must exist in the root directory of a file system for
quota-related commands to work. See quotas file and internal quotas file.
file system block The fundamental minimum size of allocation in a file system. This is equivalent
to the fragment size on some UNIX file systems.
fileset A collection of files within a file system.
fixed extent size An extent attribute used to override the default allocation policy of the file system
and set all allocations for a file to a specific fixed size.
fragmentation The on-going process on an active file system in which the file system is spread
further and further along the disk, leaving unused gaps or fragments between
areas that are in use. This leads to degraded performance because the file system
has fewer options when assigning a file to an extent.
GB Gigabyte (2
30
bytes or 1024 megabytes).
hard limit The hard limit is an absolute limit on system resources for individual users for
file and data block usage on a file system. See quota.
indirect address extent An extent that contains references to other extents, as opposed to file data itself.
A single indirect address extent references indirect data extents. A double indirect
address extent references single indirect address extents.
indirect data extent An extent that contains file data and is referenced via an indirect address extent.
Glossary244