Interpreting Hardware Paths
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| Fibre Channel Topology of HBA | ||
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| Private Loop | ||||
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| Loop and Direct Fabric Attach |
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Target |
| The value depends | For LUNs with Peripheral Device | With Peripheral Device | |||||
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| on both the Fibre | Addressing, the value of this field is | Addressing, the value of this field | |||||
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| Channel topology | the lower | is the lower | |||||
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| and the LUN | the N_Port ID of the target | of the target device. | |||||
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| addressing method | device. |
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| Arbitrated Loop Physical Address |
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| For LUNs with Logical Unit Addressing, the value is the Target field of | |||
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| the Logical Unit Number. |
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| For LUNs with Volume Set Addressing (Flat Space Addressing), the | |||
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| value is bits 3 - 6 of the Logical Unit Number. | |||
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LUN |
| The value of this field depends only on the LUN addressing method used, see below. | |||||||
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LUN |
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| Peripheral Device |
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Addressing |
| Logical Unit Addressing | |||||||
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Method |
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Value of LUN | The Target or LUN field of | The LUN field of the |
| Bits 0 - 2 of the Logical Unit | |||||
field in FC |
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| the Logical Unit Number. | Logical Unit Number. |
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HW Path |
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For more information about the fields in the Logical Unit Number, please refer to the SCSI Architecture | |||||||||
Model - 3 |
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NOTE |
| Fibre Channel devices can connect to a Fabric using either Direct Fabric Attach or Public Loop. | |||||||
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| Different devices may have different types of connections to the same Fabric, for example an | ||||||
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| HBA may have a Direct Fabric Attach connection to the Fabric, while an array has a Public | ||||||
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| Loop connection to the same Fabric. In other words, in a Fabric, the Fibre Channel Topology of | ||||||
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| an HBA may be different from the Fibre Channel Topology of devices seen by that HBA. | ||||||
Public Loop devices have an Arbitrated Loop Physical Address (AL_PA). The AL_PA usually appears in the least significant byte of the device's N_Port ID. Direct Fabric Attach devices do not have an AL_PA and the least significant byte of their N_Port ID is usually 0. This is dependent on the switch implementation and not all switches adhere to this scheme.
Some switches allow devices in Private Loop mode to connect to a Fabric. In these situations, the switch typically translates the private loop device as either a Public Loop or Direct Fabric Attach device to the rest of the Fabric. The switch also typically translates the rest of the Fabric as Private Loop devices to the Private Loop device.
Chapter 1 | 15 |
