HP-UX 11i v3 Persistent DSF Migration Guide
Introduction
In HP-UX 11i v3 HP has architected a new mass storage stack and subsystems to significantly enhance
scalability, performance, availability, manageability, and serviceability. Maximum configuration limits have
been increased to address very large SAN configurations while delivering performance with automatic load
balancing, parallel I/O scan, optimized I/O forwarding, and CPU locality.
To enhance availability, the mass storage stack monitors paths to devices, reroutes traffic and recovers from
path failures when they occur. The stack has a built-in intelligent retry algorithm on path failures and also
implements path authentication to avoid data corruption. The introduction of native multi-pathing and path-
independent persistent Device Special Files (DSFs) and the auto discovery of devices greatly enhance the
overall manageability. New commands and libraries further enhance the manageability and serviceability of
mass storage devices.
This re-architecture introduces a new representation of mass storage hardware and subsystems called the agile
view. The central idea of the agile view is that disk and tape devices are identified via their World Wide
Identifier (WWID) and not by a path to the device. Therefore in the agile representation, multiple paths to a
single device can be transparently treated as a single virtualized path, with I/O distributed across many paths.
A persistent DSF is not affected by changes in the paths to the device. To take full advantage of this agile view,
HP recommends the migration to persistent DSFs.
This white paper provides a step by step guide to ease the process of migrating applications from using legacy
DSFs to persistent DSFs. The key areas addressed in this white paper are:
Comprehensive set of links in
Read before Migrating to HP-UX 11i v3
documents
New commands and command line options to operate in the agile view
Step by Step guide on what needs to be done prior to migration
Detailed instructions on how to migrate
Possible recovery actions in case backing out is needed
For a complete overview of the mass storage changes in HP-UX 11i v3, see The Next Generation Mass Storage
Stack white paper at
http://www.hp.com/go/hpux-core-docs. Click on HP-UX 11i v3 and scroll down to the White
papers section.
Formats of DSFs and Hardware Paths for Mass Storage Devices
Legacy View
The legacy DSF format for disks is:
/dev/[r]dsk/cxtydz[sn]
Where
x is the HBA instance
y is the SCSI-2 target number
z is the SCSI-2 LUN number
n is the partition number
Example:
/dev/dsk/c5t0d1 or /dev/rdsk/c6t0d1s2
Note that the legacy DSF contains path related information. Associated with each legacy DSF is a specific
legacy hardware path, and a multi-pathed device will have multiple legacy DSFs.
Agile View
The persistent DSF format for disks introduced with the agile view in HP-UX 11i v3 is:
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