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

access control list (ACL) 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
performance, 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.
Block-Level Incremental
Backup (BLI Backup)
A Symantec 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.
contiguous file A file in which data blocks are physically adjacent on the underlying media.
data block A block that contains the actual data belonging to files and directories.
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
Glossary