Figure 17 Agile multiple path I/O stack addressing model
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| Persistent DSF |
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| Lunpath |
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| hardware path |
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| LUN |
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Legacy DSF |
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| Hardware path |
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| hardware path |
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The persistent DSF represents the device, regardless of its location in the I/O configuration. With the new model, legacy DSFs and hardware paths enjoy
The LUN hardware path is virtualized, representing all the lunpath hardware paths to a device. The lunpath hardware path is the path typically displayed in the Ignite user interface. Lunpath hardware paths do not have device special files - they are associated with a LUN hardware path and are accessed via the persistent DSF associated with a LUN hardware path. The Ignite user interface displays the lunpath hardware path so the actual device can be discerned from it; you cannot identify the physical device from looking at the LUN hardware path or the persistent DSF.
Sample agile addressing model values for the DSFs and paths are shown below.
Figure 18 Agile naming example
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| LUN |
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Persistent DSF |
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| Lunpath Hardware Path |
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| Path |
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/dev/disk/disk55 |
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| 0/0/6/0 |
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Legacy DSFs | Legacy Hardware Paths |
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| 0.0x50060b000019bc98.0x4001 |
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| 0/0/6/0 |
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/dev/dsk/c9t0d1 |
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| 0/0/6/0/0.1.18.73.0.0.1 |
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| 0.0x50060b000019c8a6.0x4001 |
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| 64000/0xfa00/0x6 |
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/dev/dsk/c11t0d1 |
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| 0/0/6/0/0.1.19.75.0.0.1 |
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| 0.0x50060b000019c8a6.0x4001 |
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| 0.0x50060b000019bc98.0x40010 |
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/dev/dsk/c17t0d1 |
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| 0/0/10/0/0.1.18.73.0.0.1 |
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| 0.0x50060b000019c8a6.0x40010 |
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/dev/dsk/c19t0d1 |
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| 0/0/10/0/0.1.19.75.0.0.1 |
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| 1/0/2/0 |
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/dev/dsk/c29t0d1 |
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| 1/0/2/0/0.1.19.75.0.0.1 |
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| 1/0/2/0 |
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/dev/dsk/c27t0d1 |
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| 1/0/2/0/0.1.18.73.0.0.1 |
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| 0.0x50060b000019bc98.0x4001 |
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| 1/0/14/0 |
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| 0.0x50060b000019c8a6.0x40010 |
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/dev/dsk/c33t0d1 |
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| 1/0/14/0/0.1.19.75.0.0.1 |
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| 0.0x50060b000019bc98.0x40010 |
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0x50060b000015330f0001000000000032 WWID LUN:
Identification of devices in a multiple path I/O configuration can be challenging. The I/O stack (driver) identifies devices using unique LUN IDs. Often this is a WWID value.
By identifying a device using the unique LUN ID, any of its hardware paths can be used to access it, and agile addressing is supported.
The unique LUN ID might be difficult for a user to associate with a specific physical or logical device. For example, often the device WWID is on a device label (e.g. on a sticker) or available via storage management software used to set up a virtual LUN – those values are difficult to remember and type correctly. It might be easier to select a device using one of its hardware paths.
72 Managing I/O for installation and recovery