Veritas Volume Manager 4.1 Administrator's Guide (HP-UX 11i v3, February 2007)

Glossary 463
path
When a disk is connected to a host, the path to the disk consists of the HBA (Host Bus
Adapter) on the host, the SCSI or fibre cable connector and the controller on the disk or
disk array. These components constitute a path to a disk. A failure on any of these results
in DMP trying to shift all I/O for that disk onto the remaining (alternate) paths. Also see
Active/Passive disk arrays, primary path and secondary path.
pathgroup
In case of disks which are not multipathed by vxdmp, VxVM will see each path as a disk.
In such cases, all paths to the disk can be grouped. This way only one of the paths from the
group is made visible to VxVM.
Persistent FastResync
A form of FastResync that can preserve its maps across reboots of the system by storing its
change map in a DCO volume on disk. Also see data change object (DCO).
persistent state logging
A logging type that ensures that only active mirrors are used for recovery purposes and
prevents failed mirrors from being selected for recovery. This is also known as kernel
logging.
physical disk
The underlying storage device, which may or may not be under VxVM control.
plex
A plex is a logical grouping of subdisks that creates an area of disk space independent of
physical disk size or other restrictions. Mirroring is set up by creating multiple data plexes
for a single volume. Each data plex in a mirrored volume contains an identical copy of the
volume data. Plexes may also be created to represent concatenated, striped and RAID-5
volume layouts, and to store volume logs.
primary path
In Active/Passive disk arrays, a disk can be bound to one particular controller on the disk
array or owned by a controller. The disk can then be accessed using the path through this
particular controller. Also see path and secondary path.
private disk group
A disk group in which the disks are accessed by only one specific host in a cluster. Also
see shared disk group.