VERITAS Volume Manager 3.5 Migration Guide (August 2002)

70 VERITAS Volume Manager Migration Guide
logical Extent
A set of logical blocks that maps to one physical extent and is a basic unit of access in a
logical volume.
LVMREC
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, thattracks outstanding mirror write
requestsand provides abasis for the resynchronization of data blocksafter asystem crash
or power failure.
physical volume
A disk that has been initialized by LVM becomes known as a physical volume.
public region
A region of a physical disk managed by VxVM that contains available space and is used
for allocating subdisks.
private region
A region of a physical disk used to store private, structured VxVM information. The
private region contains a disk header, atable of contents, and a configuration database.The
table of contents maps the contents of the disk.
physical extent
A set of physical disk blocks on a physical volume that forms a basic unit of access in
LVM. This also forms the allocation unit for logical volumes.
snapshot
A temporary extra copy (plex/mirror) created in a volume. A separate volume is created
once its contents are brought in sync with the original volume.