HP-UX 11i v3 Persistent DSF Migration Guide

Sample ioscan -m hwpath output:
Lun H/W Path Lunpath H/W Path Legacy H/W Path
====================================================================
64000/0xfa00/0x10
0/2/1/0.0x0.0x0 0/2/1/0.0.0
64000/0xfa00/0x8
0/5/1/1.0x0.0x0 0/5/1/1.0.0
64000/0xfa00/0x1a
0/2/1/1.0x0.0x0 0/2/1/1.0.0
0/5/1/0.0x0.0x0 0/5/1/0.0.0
64000/0xfa00/0x1b
0/2/1/1.0x1.0x0 0/2/1/1.1.0
0/5/1/0.0x1.0x0 0/5/1/0.1.0
The Legacy H/W path is the hardware path for the legacy DSF. The Lun H/W path is the virtualized
hardware path representing the LUN. The Lunpath H/W Path is the physical hardware path to the
LUN. The LUN under Lun H/W Path 64000/0xfa00/0x1a shows that it has two lunpaths leading to
it. Note that the last two elements of a LUN H/W path and a Lunpath H/W path use the hexadecimal
notation instead of the decimal notation.
Benefits of Migrating to the Persistent DSF Naming Model
Enhanced Features
The HP-UX 11i v3 mass storage stack provides major enhancements for performance, management,
scalability, availability, and serviceability. A major component of the new architecture is the new
persistent DSF naming model. Using persistent DSFs simplifies I/O management and diagnostics and
allows users to take full advantage of the rich set of new functionality.
Unlike legacy DSFs, persistent DSFs are path independent. Because of this a LUN can be moved
around to different paths with its persistent DSF name remaining the same. An example of this would
be moving a Fibre Channel connection into a new HBA, legacy DSFs would change but persistent DSFs
would see the new path and keep the same DSF. This feature eliminates the need for applications to
change their configuration information.
The path-independent nature of a persistent DSF offers the benefit of simplified management. Each
persistent DSF represents a LUN, unlike a legacy DSF which is really a path to a LUN. In a multi-path
environment, the number of persistent DSFs is smaller than the number of legacy DSFs. Applications do
not have to be aware of multi-pathing, simply using a persistent DSF provides multi-pathing support.
Persistent DSFs offer significant scalability over legacy DSFs. The architectural limit is 16 million LUNs
in the persistent view, versus 32,768 in the legacy view.
• Note: To enable a smooth migration from legacy to persistent DSFs, HP-UX 11i v3 supports coexistence of
both types of DSFs, and commands can display their output in either view or show the mapping, allowing
users to learn about management in the agile view while still having access to management in the legacy
view. Note also that legacy DSFs are deprecated in HP-UX 11i v3 and will be obsoleted in a future release
of HP-UX.
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