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

Glossary 237
Glossary
A
Acess Control Lists The information that
identifies specific users or groups and their access
privileges for a particular file or directory.
agent A process that manages predefined
VERITAS Cluster Server (VCS) resource types.
Agents bring resources online, take resources
offline, and monitor resources to report any state
changes to VCS. When an agent is started, it
obtains configuration information from VCS and
periodically monitors the resources and updates
VCS with the resource status.
allocation unit A group of consecutive blocks on a
file system that contain resource summaries, free
resource maps, and data blocks. Allocation units
also contain copies of the super-block.
API Application Programming Interface.
asynchronous writes A delayed write in which the
data is written to a page in the system’s page cache,
but is not written to disk before the write returns to
the caller. This improves per formance, but carries
the risk of data loss if the system crashes before the
data is flushed to disk.
atomic operation An operation that either
succeeds completely or fails and leaves everything
as it was before the operation was started. If the
operation succeeds, all aspects of the operation take
effect at once and the intermediate states of change
are invisible. If any aspect of the operation fails,
then the operation aborts without leaving partial
changes.
B
Block-Level Incremental Backup (BLI Backup)
A VERITAS backup capability that does not store
and retrieve entire files. Instead, only the data
blocks that have changed since the previous backup
are backed up.
buffered I/O During a read or write operation, data
usually goes through an intermediate kernel buffer
before being copied between the user buffer and
disk. If the same data is repeatedly read or written,
this kernel buffer acts as a cache, which can
improve performance. See unbuffered I/O and
direct I/O.
C
CFS VERITAS Cluster File System.
cluster mounted file system A shared file system
that enables multiple hosts to mount and perform
file operations on the same file. A cluster mount
requires a shared storage device that can be
accessed by other cluster mounts of the same file
system. Writes to the shared device can be done
concurrently from any host on which the cluster file
system is mounted. To be a cluster mount, a file
system must be mounted using the mount -o
cluster option. See also local mounted file system.
contiguous file A file in which data blocks are
physically adjacent on the underlying media.
CVM The cluster functionality of VERITAS
Volume Manager.
D
data block A block that contains the actual data
belonging to files and directories.