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

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root disk group A special private disk group that always exists on the system. The root disk group is
named rootdg.
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. See hard limit and quotas.
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 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. See buffered I/O and direct I/O.
volume A virtual disk which represents an addressable range of disk blocks used by applications such as file
systems or databases.
vxfs The VERITAS File System type. Used as a parameter in some commands.
VxFS The VERITAS File System.
VxVM The VERITAS Volume Manager.