Veritas Volume Manager 5.1 SP1 Administrator"s Guide (5900-1506, April 2011)

In HP-UX 11i v3, the persistent (agile) forms of such devices are located in the
/dev/disk and /dev/rdisk directories. To maintain backward compatibility,
HP-UX also creates legacy devices in the /dev/dsk and /dev/rdsk directories.
VxVM uses the device names to create metadevices in the /dev/vx/[r]dmp
directories. Dynamic Multi-Pathing (DMP) uses these metadevices (or DMP nodes)
to represent disks that can be accessed by one or more physical paths, perhaps
via different controllers. The number of access paths that are available depends
on whether the disk is a single disk, or is part of a multiported disk array that is
connected to a system.
DMP nodes are not used by the native multi-pathing feature of HP-UX.
If a legacy device special file does not exist for the path to a LUN, DMP generates
the DMP subpath name using the c#t#d# format, where the controller number in
c# is set to 512 plus the instance number of the target path to which the LUN path
belongs, the target is set to t0, and the device number in d# is set to the instance
number of the LUN path. As the controller number is greater than 512, DMP
subpath names that are generated in this way do not conflict with any legacy
device names provided by the operating system. If a DMP subpath name has a
controller number that is greater than 512, this implies that the operating system
does not provide a legacy device special file for the device.
You can use the vxdisk utility to display the paths that are subsumed by a DMP
metadevice, and to display the status of each path (for example, whether it is
enabled or disabled).
See “How DMP works” on page 141.
Device names may also be remapped as enclosure-based names.
See “Disk device naming in VxVM” on page 79.
Disk device naming in VxVM
Device names for disks are assigned according to the naming scheme which you
specify to VxVM. The format of the device name may vary for different categories
of disks.
See “Disk categories” on page 85.
Device names can use one of the following naming schemes:
■ Operating system-based naming
■ Enclosure-based naming
Devices with device names longer than 31 characters always use enclosure-based
names.
79Administering disks
Disk devices