Ignite-UX Administration Guide for HP-UX 11i (B3921-90079, October 2013)

Recovery and the Agile View
During recovery, Ignite-UX C.7.x makes changes to the new system I/O configuration to match
the original system I/O configuration. This is necessary because some aspects of a system
configuration depend on the unpredictable order of system I/O inventory.
The overall goal of this process is to make the system I/O configuration appear as if the system
simply rebooted at the time the recovery archive was created. This process is complex, and Ignite-UX
might be unable to fully restore the I/O configuration. Ignite might not be able to restore aspects
of the I/O configuration due to hardware changes, limitations of system I/O software, and limitations
of Ignite-UX.
The system I/O configuration should be verified during and after recovery so configuration
adjustments can be made if needed.
One part of restoring the I/O configuration is the appropriate matching of device special files
(DSFs) and devices. There is one approach used for legacy DSFs in HP-UX 11i v3 and previous
releases, and another approach used for HP-UX 11i v3 persistent DSFs.
Legacy DSFs and Device Matching
Matching legacy DSFs and mass storage devices is done based on hardware paths. Generally,
legacy DSFs are associated with a particular hardware path. During recovery, a device is associated
with its hardware path's DSF. (See Figure 16 (page 71) for a description of the legacy addressing
model.)
Hardware configuration changes are handled by assuming a new device is intended to replace
the device originally at that hardware path.
Note that some I/O protocols, such as SAS and USB, associate legacy DSFs with specific devices
using unique LUN IDs, and so behave like persistent DSF matching described below.
SAS devices are a special case, since their legacy DSF/unique LUN ID association can change
as a result of I/O configuration changes. If you change a SAS configuration (physically move a
SAS device to another bay or remove a SAS device) the hardware path associated with that and
other SAS devices can change during an installation or recovery. In such a case, hardware paths
are reassigned to SAS devices. Since legacy DSFs are associated with a particular hardware path,
a change in a device's hardware path breaks the association between its previous legacy DSF
and its unique LUN ID. Note that the way SAS devices are associated during recovery might
change in future versions of Ignite-UX to use the agile addressing approach described below.
Only certain SAS configuration changes cause remapping of hardware paths. For more information
see the white paper, “Ignite-UX and SAS Devices” available at http://www.hp.com/go/
ignite-ux-docs.
Persistent DSFs and Device Matching
Matching persistent DSFs and mass storage devices is relatively complex due to agile addressing.
Ignite-UX will attempt to simulate agile addressing during recovery, while also dealing with hardware
replacement. This matching is accomplished using the methods described below:
• WWID — Matching is done based on the unique LUN ID of the device. Most often, this is the
device's WWID. This method matches a device's original persistent DSF with the same device
in the recovered system configuration.
• Device ID — (Future) Matching is done based on a user-definable identifier written to the
device. This method matches a device's original persistent DSF with the device that has the
same device ID in the recovered system configuration. This method allows user-provided
identification to control device matching. Note that some mass storage devices do not support
the device ID feature.
• Physical Location — Matching is done based on device physical location. This method matches
the original persistent DSF associated with a particular physical location (e.g. same enclosure
80 Managing I/O for Installation and Recovery