1 HV Installation and Operations Guide

36 Host Device Configuration Chapter 2

Host Device Configuration

The host system using a Fibre Channel host bus adapter (HBA) will typically

map Fibre Channel devices into the existing device mapping scheme used by

that operating system. (Refer to the HBA manual for the mapping table.) The

Fibre Channel HBA usually maps Fibre Channel AL_PAs to SCSI target

addresses. The HBA will claim enough SCSI bus entries to allow for 125 Fibre

Channel targets to map to SCSI bus:target entries. This is usually done by a

fixed mapping of AL_PA to bus:target. In such a configuration, the bridge

corresponds to a bus:target identifier, with the SCSI devices attached to the

bridge appearing as logical units (LUNs). In addition, operating systems can

extend the available SCSI limit of 15 Target IDs per bus.

Although this is not an issue for the operating system or most applications,

there are cases where older applications or Windows NT can have

expectations about what are valid SCSI IDs, and not deal correctly with certain

mappings. In particular, applications have been seen to exhibit difficulties

addressing Target IDs greater than 15 (e.g. 16 and up). This problem can be

resolved by configuring the bridge to use hard addressing, and setting the

AL_PA used by the bridge to a value that the HBA will map to, with an ID

having a value less than 16.