HP Tape Library Interface Manager Software - Manual (Page 32)

32 Choosing the Right Configuration Chapter 2
Auto-Indexed Mapping
This is the default method of operation. Discovery of SCSI devices is performed
at every startup (power up, or reboot). As devices are discovered, they are
added to the FC-to-SCSI mapping table. The FC LUN numbers are assigned
sequentially. The mapping table is stored in FLASH memory. An example of a
FC-to-SCSI map for three SCSI devices is shown in Table 1 .
In this method, the host system detects every attached device without voids in
the FCP LUN list, allowing full device discovery to the host. This allows easy
configuration in environments where device ordering is not important, and hot
plugging of SCSI devices will not occur.
Fixed-Indexed Mapping
This is an optional method of operation. Although the interface performs
discovery of SCSI devices at startup, the results of this discovery are not utilized
to create the FC-to-SCSI mapping table. Instead, the copy of the mapping table
stored in FLASH memory is used.
Fixed-indexed is recommended for environments where SCSI device
configurations may change, and a fixed mapping from the application to the
target device is required. That is, if a SCSI device is removed from the SCSI
bus, and the fibre interface is power cycled or rebooted, then the FC-to-SCSI
addressing for the remaining SCSI devices will not change. The SCSI device
can be replaced at the same address. An example of such an environment is
where hot pluggable devices may be used.
Table 1 Example of a Fibre Channel-to-SCSI Mapping
Fibre Channel SCSI
FCP LUN Bus Target LUN
0 0 0 0
1 0 1 0
2 1 2 0