HP-UX 11i v3 Native Multi-Pathing for Mass Storage (August 2012)

11
• Newly discovered active lunpaths are automatically used in the lunpath selection scheme of I/O
load balancing. Therefore, applications sending I/O operations through existing LUN DSFs are not
affected by the discovery of new lunpaths.
• New LUN DSFs corresponding to newly discovered LUNs are seemlessly created.
SAN component deletion
Throughout the life of a system, SAN components may be replaced or removed. For instance,
lunpaths to a LUN device may become stale because the target port involved has been replaced.
Administrators can delete SCSI target paths and SCSI lunpaths using rmsf. They can also replace
and delete SCSI controllers using the OL* process.
The I/O stack transparently handles deletion or disabling of lunpaths. As long as there is at least one
available lunpath to a LUN, I/O traffic is not affected. This enables customers to replace faulty SCSI
HBAs (with OL* operations) or faulty SCSI target ports without impacting applications. For more
information, see rmsf(1M) and pdweb(1M).
Easy monitoring of LUNs and lunpaths accessiblity
To provide administrators with a real-time status of the availability of lunpath or a LUN components,
the mass storage subsystem dynamically updates the health property of lunpath and LUN I/O
nodes. The health property conveys availability status values such as online, offline, unusable,
disable, or standby. Without performing a full scan of the SAN configuration, the administrator can
display the health property of lunpaths and LUN components by running ioscan -P health.
For more information, see
Lunpath and LUN health.
Full integration with HP-UX 11i v3
Multi-pathing is fully integrated with HP-UX 11i v3. Here are a few examples of subsystems and
utilities that have evolved toward using multi-pathing.
crashconf(1M)
The dump subsystem is aware of multi-pathed devices and supports automatic dump device path
failover. If a configured lunpath goes offline, the dump subsystem automatically selects an alternate
available hardware lunpath and reconfigures the dump device. The dump subsystem also takes
advantage of multi-pathing through the concurrent dump functionality, which significantly reduces
dump time.
For more information on changes to the dump subsystem, see the
HP-UX 11i v3 Crash Dump
Improvement white paper.
setboot(1M)
The setboot command is aware of multi-pathed devices and supports automatic boot path failover.
If the hardware lunpath written into stable storage goes offline, setboot retrieves an alternate
available lunpath to the LUN and writes it into the system stable storage.
For more information, see the
setboot(1M) in HP-UX 11i v3 white paper.
LVM
In the HP-UX 11i v3 release, LVM supports both legacy and persistent DSFs. Because multi-pathing
applies by default to legacy and persistent LUN DSFs, LVM uses native multi-pathing by default.
All the LVM commands (
pvcreate, vgcreate, and vgextend) are backward compatible, and work
transparently with both legacy and persistent DSFs. New options have been added
to vgimport and
vgscan to select the persistent DSF naming model. HP highly recommends using persistent DSFs for
LVM configurations. The LVM alternate links (PVlinks) feature is still supported in HP-UX 11i v3.