Overview: The Next Generation Mass Storage Stack (September 2009)

Hardware Path Details
This section contains more information about the hardware paths shown in the Legacy View and Agile View.
In HP-UX 11i v3, there are three different types of paths to a device: legacy hardware path, lunpath hardware
path, and LUN hardware path. All three are numeric strings of hardware components, with each number typically
representing the location of a hardware component on the path to the device.
Legacy hardware
path
This is the format used in releases prior to HP-UX 11i v3. It is displayed in the legacy view.
It is composed of a series of bus-nexus addresses separated by a slash (/) leading to the
HBA. Beyond the HBA, additional address elements are separated by a period (.).
For parallel SCSI devices, the addressing is a simple target and LUN as follows:
0/1/1/0.1.0
For Fibre Channel devices, legacy addressing is emulated with a domain, area, port, virtual
bus, virtual target, and virtual LUN as follows:
0/2/1/0.1.6.0.0.2.1
Lunpath hardware
path
This format enables the use of more targets and LUNs than are permitted under legacy
hardware paths. It is printed in the agile view. Its format is identical to a legacy hardware
path up to the HBA, and represents the same path to the LUN. Beyond the HBA, additional
elements are printed in hexadecimal notation and separated by a period (.). The leading
elements represent a transport-dependent target address. The final element is a LUN
address, a 64-bit representation of the LUN identifier reported by the target.
The following lunpath hardware path uses the Fibre Channel transport:
0/2/1/0.0x50001fe1500170ac.0x4017000000000000
The following lunpath hardware path uses parallel SCSI:
0/1/1/0.0xd.0x0
For more specifics on the components of a lunpath hardware path, see
Appendix D:
Interpreting Lunpath Hardware Paths.
LUN hardware
path
This format is a virtualized path that represents all the lunpaths to a single LUN. It is printed
in the agile view. Instead of a series of bus-nexus addresses leading to the HBA, the path
contains a virtual bus-nexus (called the virtual root node) with an address of 64000.
Addressing beyond the virtual root node consists of a virtual bus address and a virtual LUN
ID, delimited by slash (/) characters. An example of a LUN hardware path is as follows:
64000/0xfa00/0x22
As a virtualized path, the LUN hardware path is only a handle to the LUN and does not
represent the LUN physical location. Instead it is based on the LUN WorldWide Identifier
(WWID). It remains the same if new physical paths to the device are added, if existing
physical paths are removed, or if a physical path changes. This LUN binding persists across
reboots, but it is not guaranteed to persist across installations. Reinstalling a system or
installing an identically configured system can create a different set of LUN hardware paths.
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