IBM DS4800 - Fibre channel loop and ID settings

d. Connect drive port 4 (drive channel 1) of controller A to the In port on the
left ESM board of the first storage expansion enclosure in the group. (See
callout 1 in Figure 44.)
e. Connect drive port 1 (drive channel 3) of controller B to the Out port on the
right ESM board of the last storage expansion enclosure in the group. (See
callout 5 in Figure 44.)
You have now completed the redundant fibre channel cabling of the first group
of storage expansion enclosures to the DS4800, using the first ports of the
dual-ported drive channels 1 and 3.
For EXP810 storage expansion enclosure connections:
Figure 44. Connecting EXP710 or EXP100 enclosures to DS4800
64 IBM System Storage DS4800 Storage Subsystem: Installation, User’s, and Maintenance Guide