Dell PowerVault 35F (Fibre Channel Bridge) - Manual (Page 20)

Understanding the PowerVault 35F Configuration: Dell PowerVault 35F User's Guide
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is at least one address available on the loop that is connected to the PowerVault 35F. Fibre Channel supports up to 126
devices on an arbitrated loop.
Hard Addressing
When acquiring a hard address, the PowerVault 35F attempts to acquire the AL_PA value that was specified by user
configuration. If the desired address is not available at loop initialization time, the PowerVault 35F comes up on the
loop in non-participating mode. This allows the loop to continue to operate, although the unit will not be accessible via
the Fibre Channel interface. This would occur when another device on the arbitrated loop has acquired the same
address as that configured on the PowerVault 35F.
Hard addressing is recommended for environments where it is important that the device addresses do not change.
Device address changes can affect the mapping represented by the host operating system to the application, and have
adverse effects. An example of such an environment would be a tape library installation, where the application
configuration requires fixed device identification for proper operation. Hard addressing will insure that the device
identification to the application will remain constant.
When connected to a Fibre Channel Switch, the PowerVault 35F is identified to the switch as a unique device by the
factory programmed World Wide Name (WWN). No further configuration is needed, although the WWN can be
configured to a user-defined value through the configuration interface.
General SCSI Configuration
The PowerVault 35F appears on each SCSI bus as a single initiator. The default initiator ID is 7, and can be set via
configuration to any valid SCSI address. No other devices on the SCSI bus may use this address.
The PowerVault 35F provides the capability to reset the SCSI buses during the boot cycle. This allows the devices on a
SCSI bus to be in a known state. Configuration allows this feature to be enabled or disabled. This feature is enabled in
the default configuration. Configurations using multiple devices that have long reset cycles, or are adversely affected
by bus resets, should disable this feature.
The PowerVault 35F negotiates for the maximum values for transfer rates and data width on a SCSI bus. If an attached
device does not allow the full rates, the unit will use the rates negotiated for that device. Negotiation is on a device
specific basis, so the unit can support a mix of device types on the same bus.
Fibre Channel Host to SCSI Target Configuration
This section describes the configuration of the PowerVault 35F when acting as a target to a Fibre Channel Initiator,
passing Fibre Channel Protocal (FCP) requests through to SCSI target devices.
This is configured as the default, using soft addressing on the Fibre Channel loop and auto addressing for the target
device mapping. Auto addressing is described further in this section.
The PowerVault 35F automatically detects if it is connected to an FL or F_Port, and will use the appropriate type
without further configuration.
Address Mapping
The PowerVault 35F supports three addressing methods for mapping SCSI targets to Fibre Channel Hosts: