VERITAS Volume Manager 4.1 Administrator's Guide

Glossary
disk media name
Glossary 431
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 procedure by
which the VxVM monitors and logs
modifications to a plex. A bitmap of changed
regions is kept in 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.
disk A collection of read/write data blocks
that are indexed and can be accessed fairly
quickly. Each disk has a universally unique
identifier.
disk access name An alternative term for a
device name.
disk access records Configuration records
used to specify the access path to particular
disks. Each disk access record contains a
name, a type, and possibly some type-specific
information, which is used by VxVM in
deciding how to access and manipulate the
disk that is defined by the disk access record.
disk array A collection of disks logically
arranged into an object. Arrays tend to
provide benefits such as redundancy or
improved performance. Also see disk
enclosure and JBOD.
disk array serial number This is the
serial number of the disk array. It is usually
printed on the disk array cabinet or can be
obtained by issuing a vendor- specific SCSI
command to the disks on the disk array. This
number is used by the DMP subsystem to
uniquely identify a disk array.
disk controller In the multipathing
subsystem of VxVM, the controller (host bus
adapter or HBA) or disk array connected to
the host, which the Operating System
represents as the parent node of a disk.
disk enclosure An intelligent disk array
that usually has a backplane with a built-in
Fibre Channel loop, and which permits
hot-swapping of disks.
disk group A collection of disks that share
a common configuration. A disk group
configuration is a set of records containing
detailed information on existing VxVM
objects (such as disk and volume attributes)
and their relationships. Each disk group has
an administrator-assigned name and an
internally defined unique ID. The root disk
group (rootdg) is a special private disk group
that always exists.
disk group ID A unique identifier used to
identify a disk group.
disk ID A universally unique identifier that
is given to each disk and can be used to
identify the disk, even if it is moved.
disk media name An alternative term for a
disk name.