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

7 Managing I/O for Installation and Recovery
This chapter introduces Ignite-UX I/O concepts and describes how multi-path concepts enhance
Ignite-UX. This chapter also assists the user moving from the legacy naming model to the agile
naming model by touching on changes found in multi-path aware Ignite.
Introducing Multipathing
In its current implementation, beginning with C.7.1.x, Ignite-UX is aware of multiple paths to I/O
devices. Ignite-UX now supports agile view on HP-UX 11i v3.
One of the features of HP-UX 11i v3 and later is the ability to tolerate I/O path changes. For HP-UX
11i v2 and earlier releases of HP-UX, Ignite-UX is aware that multiple device special files (DSFs)
and hardware paths may refer to the same device logical unit (LUN).
Previous to HP-UX 11i v3, I/O addressing looks like Figure 16, where a DSF is specific to one
hardware path, which in turn points to an I/O device’s LUN.
Figure 16 Legacy I/O Stack Addressing Model
LUN
Legacy DSFs Legacy Hardware Paths
/dev/dsk/c9t0d1
0/0/6/0/0.1.18.73.0.0.1
/dev/dsk/c11t0d1
0/0/6/0/0.1.19.75.0.0.1
/dev/dsk/c17t0d1
0/0/10/0/0.1.18.73.0.0.1
/dev/dsk/c19t0d1
0/0/10/0/0.1.19.75.0.0.1
/dev/dsk/c29t0d1
1/0/2/0/0.1.19.75.0.0.1
/dev/dsk/c27t0d1
1/0/2/0/0.1.18.73.0.0.1
/dev/dsk/c37t0d1
1/0/14/0/0.1.18.73.0.0.1
/dev/dsk/c33t0d1
1/0/14/0/0.1.19.75.0.0.1
Any of the legacy DSFs can be used to access the I/O device. Care must be taken to prevent the
simultaneous use of multiple DSFs for conflicting purposes. For example, two DSFs for the same
LUN might be used for different volume or disk groups. Ignite-UX will detect such an invalid
configuration created with the Ignite user interface and prevent installation. A final validation is
also done during sanity checking, which takes place after starting an installation.
Agile View Concepts
Starting with HP-UX 11i v3, HP-UX is aware of multiple paths to devices and provides multipathing
functionality automatically. Important new concepts related to this functionality are: persistent DSF,
LUN hardware path, lunpath hardware path, device identifier, and agile addressing.
Agile view I/O addressing logic looks like Figure 17.
Introducing Multipathing 71