Veritas Volume Manager 5.1 SP1 Administrator"s Guide (5900-1506, April 2011)

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.
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/O for that disk onto the remaining
(alternate) paths.
pathgroup In the case of disks which are not multipathed by vxdmp, VxVM will see each path
as a disk. In such cases, all paths to the disk can be grouped. This way only one of
the paths from the group is made visible to VxVM.
565Glossary