VERITAS File SystemÖ 3.5 (HP OnlineJFS/JFS3.5) AdministratorÆs Guide (December 2002)

148
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/fstab 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.
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 quotas.
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.
inode A unique identifier for each file within a file system that contains the data and metadata associated
with that file.
inode allocation unit A group of consecutive blocks containing inode allocation information for a given
fileset. This information is in the form of a resource summary and a free inode map.
intent logging A method of recording pending changes to the file system structure. These changes are
recorded in a circular intent log file.
internal quotas file VxFS maintains an internal quotas file for its internal usage. The internal quotas file
maintains counts of blocks and indices used by each user. See quotas and external quotas file.
K Kilobyte (2
10
bytes or 1024 bytes).
large file A file larger than two gigabytes. VxFS supports files up to two terabytes in size.
large file system A file system more than two gigabytes in size. VxFS supports file systems up to two
terabytes in size.