VERITAS Volume Manager 3.1 Administrator's Guide

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node join The process through
which a node joins a cluster and
gains access to shared disks.
object An entity that is defined to
and recognized internally by the
Volume Manager. 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 Thestandard division of
a physical disk device, as
supporteddirectly by the operating
system and disk drives.
path When a disk is connected to a
host, the path to the disk consists
of the HBA (Host Bus Adapter) on
the host, the SCSI or fibre cable
connector and the controller on the
disk or disk array. These
components constitute a path to a
disk. A failure on any of these
results in DMP trying to shift all
I/Os for that disk onto the
remaining(alternate) paths.
persistent state logging A
logging type thatensures that only
active mirrors are used for
recovery purposes and prevents
failed mirrors from being selected
for recovery. This is also known as
kernel logging.
physical disk The underlying
storage device, which may or may
not be under Volume Manager
control.
plex A duplicate copy of a volume
and the data therein (in the form of
an ordered collection of subdisks).
Each plex is one copy of the volume
with which the plex is associated.
The terms mirror and plex can be
used synonymously.