Veritas Volume Manager 5.0 Administrator's Guide (September 2006)

508 Glossary
A set of hosts (each termed a node) that share a set of disks.
cluster manager
An externally-provided daemon that runs on each node in a cluster. The cluster managers on each
node communicate with each other and inform VxVM of changes in cluster membership.
cluster-shareable disk group
A disk group in which access to the disks is shared by multiple hosts (also referred to as a shared disk
group). Also see private disk group.
column
A set of one or more subdisks within a striped plex. Striping is achieved by allocating data alternately
and evenly across the columns within a plex.
concatenation
A layout style characterized by subdisks that are arranged sequentially and contiguously.
configuration copy
A single copy of a configuration database.
configuration database
A set of records containing detailed information on existing VxVM objects (such as disk and volume
attributes).
data change object (DCO)
A VxVM object that is used to manage information about the FastResync maps in the DCO volume.
Both a DCO object and a DCO volume must be associated with a volume to implement Persistent
FastResync on that volume.
data stripe
This represents the usable data portion of a stripe and is equal to the stripe minus the parity region.
DCO volume
A special volume that is used to hold Persistent FastResync change maps, and dirty region logs (see
dirty region logging).
detached
A state in which a VxVM object is associated with another object, but not enabled for use.
device name
The device name or address used to access a physical disk, such as c0t0d0. The c#t#d# syntax
identifies the controller, target address, and disk. In a SAN environment, it is more convenient to use
enclosure-based naming, which forms the device name by concatenating the name of the enclosure
(such as enc0) with the disk’s number within the enclosure, separated by an underscore (for
example, enc0_2). The term disk access name can also be used to refer to a device name.
dirty region logging
The method by which the VxVM monitors and logs modifications to a plex as a bitmap of changed
regions. For a volumes with a new-style DCO volume, the dirty region log (DRL) is maintained in the
DCO volume. Otherwise, the DRL is allocated to an associated subdisk called a log subdisk.
disabled path
A path to a disk that is not available for I/O. A path can be disabled due to real hardware failures or if
the user has used the vxdmpadm disable command on that controller.