VERITAS Volume Manager 4.1 Administrator's Guide

Glossary
partition
Glossary 433
initiating node The node on which the
system administrator is running a utility
that requests a change to VxVM objects. This
node initiates a volume reconfiguration.
JBOD The common name for an
unintelligent disk array which may, or may
not, support the hot-swapping of disks. The
name is derived from “just a bunch of disks.”
log plex A plex used to store a RAID-5 log.
The term log plex may also be used to refer
to a Dirty Region Logging plex.
log subdisk A subdisk that is used to store
a dirty region log.
master node A node that is designated by
the software to coordinate certain VxVM
operations in a cluster. Any node is capable
of being the master node.
mastering node The node to which a disk
is attached. This is also known as a disk
owner.
mirror A duplicate copy of a volume and
the data therein (in the form of an ordered
collection of subdisks). Each mirror consists
of one plex of the volume with which the
mirror is associated.
mirroring A layout technique that mirrors
the contents of a volume onto multiple
plexes. Each plex duplicates the data stored
on the volume, but the plexes themselves
may have different layouts.
multipathing Where there are multiple
physical access paths to a disk connected to a
system, the disk is called multipathed. Any
software residing on the host, (for example,
the DMP driver) that hides this fact from the
user is said to provide multipathing
functionality.
node One of the hosts in a cluster.
node abort A situation where a node leaves
a cluster (on an emergency basis) without
attempting to stop ongoing operations.
node join The process through which a
node joins a cluster and gains access to
shared disks.
Non-Persistent FastResync A form of
FastResync that cannot preserve its maps
across reboots of the system because it stores
its change map in memory.
object An entity that is defined to and
recognized internally by VxVM. The VxVM
objects are: volume, plex, subdisk, disk, and
disk group. There are actually two types of
disk objects—one for the physical aspect of
the disk and the other for the logical aspect.
parity A calculated value that can be used
to reconstruct data after a failure. While
data is being written to a RAID-5 volume,
parity is also calculated by performing an
exclusive OR (XOR) procedure on data. The
resulting parity is then written to the
volume. If a portion of a RAID-5 volume
fails, the data that was on that portion of the
failed volume can be recreated from the
remaining data and the parity.
parity stripe unit A RAID-5 volume
storage region that contains parity
information. The data contained in the
parity stripe unit can be used to help
reconstruct regions of a RAID-5 volume that
are missing because of I/O or disk failures.
partition The standard division of a
physical disk device, as supported directly by
the operating system and disk drives.