IBM TotalStorage DS300 Best Practices Manual page 482

e. Depending on the planning it is possible not to choose a specific target
and LUN to boot from The adapter has the functionality to decide from
which LUN0 the system will boot. As long as only one storage subsystem
is attached to this system there are no problems. With multiple storage
systems attached multiple different LUN0 may exist. This can lead to boot
problems when a LUN0 from the wrong storage system is chosen to boot
from. The next steps explain how to select s specific target and device to
boot from.
f. Select (Primary) Boot Port Name and LUN and press Enter.
Figure 9-24 Primary Boot Port and LUN
g. Select the target which owns the logical drive to boot from. Than press
Enter. In this case the logical drive is owned by controller A. The initiator is
allowed only to access port FC0 of controller A. The third and fourth digit
characterize the port on the Total Storage DS400. 00 represents FC0 on
controller A, 01 represents FC1 on controller A, 02 represents FC0 on
controller B and 03 represents FC1 on controller B. Other ports of the
TotalStorage DS400 do not provide in the current configuration LUNs.
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IBM TotalStorage DS300 and DS400 Best Practices Guide