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

Glossary
data synchronous writes
Glossary238
data synchronous writes A form of synchronous
I/O that writes the file data to disk before the write
returns, but only marks the inode for later update. If
the file size changes, the inode will be written
before the write returns. In this mode, the file data
is guaranteed to be 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 also
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.
E
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 also quotas
file and internal quotas file..
F
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.
G
GB Gigabyte (230 bytes or 1024 megabytes).
H
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 also quota.