IBM System Storage Subsystem DS5020 - Manual (Page 105)

5. Connect port 1A on the left ESM in EXP520 two to port 1B on the left ESM in
EXP520 four.
6. Connect port 1A on the right ESM in the EXP520 four to port 1B on the right
ESM in EXP520 two.
7. Connect port 1B on the left ESM in EXP520 two to port 1 of drive channel 1 on
the DS5020.
8. Connect port 2 of drive channel 2 on the DS5020 to port 1B on the right ESM in
the EXP520 four.
Figure 50 on page 76 shows the cabling scheme for one DS5020 storage
subsystem and a maximum of six EXP520 storage expansion enclosures behind
both ports of a dual-ported drive channel.
Chapter 3. Cabling the storage subsystem 75