Veritas Storage Foundation 5.1 SP1 Cluster File System Administrator"s Guide (5900-1738, April 2011)

shared disk group A disk group in which the disks are shared by multiple hosts (also referred to as
a cluster-shareable disk group).
shared volume A volume that belongs to a shared disk group and is open on more than one node
at the same time.
snapshot file system An exact copy of a mounted file system at a specific point in time. Used to do
online backups.
snapped file system A file system whose exact image has been used to create a snapshot file system.
soft limit The soft limit is lower than a hard limit. The soft limit can be exceeded for a limited
time. There are separate time limits for files and blocks.
Storage Checkpoint A facility that provides a consistent and stable view of a file system or database
image and keeps track of modified data blocks since the last Storage Checkpoint.
structural fileset The files that define the structure of the file system. These files are not visible or
accessible to the user.
super-block A block containing critical information about the file system such as the file
system type, layout, and size. The VxFS super-block is always located 8192 bytes
from the beginning of the file system and is 8192 bytes long.
synchronous writes A form of synchronous I/O that writes the file data to disk, updates the inode
times, and writes the updated inode to disk. When the write returns to the caller,
both the data and the inode have been written to disk.
TB (terabyte) 2
40
bytes or 1024 gigabytes.
transaction Updates to the file system structure that are grouped together to ensure they are
all completed.
throughput For file systems, this typically refers to the number of I/O operations in a given
unit of time.
unbuffered I/O I/O that bypasses the kernel cache to increase I/O performance. This is similar to
direct I/O, except when a file is extended; for direct I/O, the inode is written to
disk synchronously, for unbuffered I/O, the inode update is delayed.
VCS (Veritas Cluster
Server)
volume A virtual disk which represents an addressable range of disk blocks used by
applications such as file systems or databases.
volume set A container for multiple different volumes. Each volume can have its own
geometry.
vxfs The Veritas file system type. Used as a parameter in some commands.
VxFS The Veritas File System.
205Glossary