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

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

 

 

 

 

 

 

 

 

 

 

 

LUN

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

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