Glossary

AIX coexistence label

Data on disk which identifies the disk to the AIX volume manager (LVM) as being controlled by VxVM. The contents has no relation to VxVM ID Blocks.

back-rev disk group

A disk group created using a version of VxVM released prior to the release of CDS. Adding CDS functionality rolls over to the latest disk group version number; see also current-rev disk group.

CDS (Cross-platform Data Sharing)

Sharing data between heterogeneous systems (such as Solaris and HP-UX operating systems), where each system has direct access to the physical devices used to hold the data, and understands the data on the physical device. Sharing in this sense should not be confused with the sharing provided with CVM by means of a shared disk group.

CDS disk

A disk whose contents and attributes are such that the disk can be used for CDS as part of a CDS disk group. In contrast, a non-CDS disk cannot be used for CDS, nor can it be part of a CDS disk group. CDS disk also contains a set of AIX Coexistence Labels, HP-UX Coexistence Labels/VxVM ID Blocks, and Platform Blocks.

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CDS disk group

A VxVM disk group whose contents and attributes are such that the disk group can be used to provide CDS. In contrast, a non-CDS disk group (that is, a back-rev disk group or a current-rev disk group) cannot be used for CDS. A CDS disk group is a current-rev disk group with the CDS attribute set for the disk group. A CDS disk group can only contain CDS disks.

CFS

Cluster file system. A VxFS file system mounted on a selected volume in cluster (shared) mode.

children

Objects that belong to an object group.

cluster

A set of host machines (nodes) that shares a set of disks.

cluster file system

See CFS.

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current-rev disk group

A disk group created using a version of VxVM providing CDS functionality; however, the CDS attribute is not set. If the CDS attribute is set for the disk group, the disk group is called a CDS disk group.

data change object

See DCO.

DCO (Data Change Object)

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.

DCO volume

A special volume that is used to hold Persistent FastResync change maps, and dirty region logs (see dirty region logging). The map layout within the DCO volume changed with the release of VxVM 4.0, although the original format is still available. The old layout is available in DCO Version 0 objects, and the new layout is available in DCO Version 20 objects.

device name

The physical disk device name (or disk access name).

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dirty region logging

See DRL.

disk access name

The device name or address that is used to access a physical disk on an operating system, such as hdisk1 (AIX), c0t0d0 (HP-UX), sda (Linux), or c0t0d0s2 (Solaris OS). 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).

disk group

A set of disks that are under VxVM control and share a common configuration. A disk group configuration is a set of records containing detailed information on existing VERITAS Volume Manager objects (such as disk and volume attributes) and their relationships. Each disk group has an administrator-assigned name. Volumes can only be created on disks that belong to disk groups.

disk media name

A logical or administrative name chosen for a disk that is under the control of VxVM, such as disk03. Also referred to a disk name.

DRL (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 is maintained in the DCO volume. Otherwise, the dirty region log is allocated to an associated subdisk called a log subdisk.

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encapsulation

A process that converts existing partitions on a specified disk to volumes. If any partitions contain file systems, /etc/fstab entries are modified so that the file systems are mounted on volumes instead. This feature is only supported on the Linux and Solaris operating systems.

enclosure

A disk array.

gap

A disk region that does not contain VERITAS Volume Manager objects (subdisks).

HP-UX coexistence label

Data on disk which identifies the disk to the HP volume manager (LVM) as being controlled by VxVM. The contents of this label are identical to the contents of the VxVM ID block.

mirror

A copy of a volume and its data. There can be several mirrors per volume. The terms mirror and plex are used synonymously.

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node

In the VxVM tree, a node is an element attached to the tree.




In a cluster environment, a node is a host machine in a cluster.

object group

A group of objects of the same type. Each object group has a group icon and a group name. In VxVM, object groups include disk groups, disks, volumes, controllers, free disk pool disks, uninitialized disks, and file systems.

object tree

A dynamic hierarchical display of VERITAS Volume Manager objects and other objects on the system. Each node in the tree represents a group of objects of the same type.

platform block

Data placed in sector 0, which contains OS-specific data for a variety of platforms that require its presence for proper interaction with each of those platforms. The platform block allows a disk to masquerade as if it was initialized by each of the specific platforms.

plex

A copy of a volume and its data. There can be several plexes per volume. The terms mirror and plex are used synonymously.

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private region

A region of a physical disk used to store private, structured VxVM information. The private region contains a disk header, a table of contents, and a configuration database. The table of contents maps the contents of the disk. The disk header contains a disk ID. All data in the private region is duplicated for extra reliability.

public region

A region of a physical disk managed by VxVM that contains available space and is used for allocating subdisks.

sector size

Sector size is an attribute of a disk drive (or SCSI LUN for an array-type device), which is set when the drive is formatted. Sectors are the smallest addressable unit of storage on the drive, and are the units in which the device performs I/O.

subdisk

A set of contiguous disk blocks that form a logical disk segment. Subdisks are associated with plexes (mirrors) to form volumes.

uninitialized disks

Disks that are not under VxVM control.

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volume

A virtual disk or entity that is made up of portions of one or more physical disks.

VxFS

VERITAS File System.

VxVM

VERITAS Volume Manager.

VxVM ID block

Data on disk that indicates the disk is under VxVM control. The VxVM ID Block provides dynamic VxVM private region location, GUID, and other information.