VERITAS Volume Manager 5.0 Migration Guide (September 2006)

Glossary
block
A unit of space for data on a disk, typically having a size of 1024-bytes.
Dirty Region Logging
Dirty Region Logging (DRL) is an optional property of a volume, used to provide a speedy recovery
of mirrored volumes after a system failure. DRL keeps track of the regions that have changed due to
I/O writes to a mirrored volume.
file system
The organization of files on storage devices. The term file system can refer either to the entire file
system or to a subsection of that file system, contained within a disk section or a logical volume that
can be mounted or unmounted from that tree.
logical volume
A logical structure that is a map of storage areas on physical volumes. A logical volume can be
conceptualized as a storage device of flexible size. The data in a logical volume can be mapped to one
or more physical volumes. A virtual disk device that represents a contiguous virtual disk space that
maps to single or multiple areas on a single or multiple physical volumes.
LVM
The Logical Volume Manager (LVM) is a subsystem for managing disk space. LVM is an HP-UX
product, similar to VxVM.
LIF
The Logical Interchange Format (LIF) is a HP mass-storage format that can be used for interchange
of files among various HP computer systems. Each boot disk has a LIF directory that contains boot
programs.
logical Extent
A set of logical blocks that maps to one physical extent and is a basic unit of access in a logical
volume.
LVM REC
The LVM record, which is an identifier that is set on each disk when it is initialized the first time by
LVM. There are two copies of the LVMREC; one is at sector 8, while the other is at sector 72.
mirror disk/UX
HP-UX software product that allows disk mirroring as part of LVM functionality. Mirror Disk/UX
allows up 2 mirror copies in a volume.
Mirror Write Cache (MWC)
A MirrorDisk/UX mechanism whose use is optional, that tracks outstanding mirror write requests and
provides a basis for the resynchronization of data blocks after a system crash or power failure.
physical volume