Lenovo DM120S Installation And Cabling Manual page 29

Multipath HA with four onboard SAS ports and two single-shelf stacks
The following worksheet and cabling example uses port pairs 0a/0d and 0c/0b:
Multipath HA with four onboard SAS ports, a quad-port SAS HBA, and two multi-shelf stacks
Four port pairs are available for this configuration: 0a/1b, 1a/0d, 0c/1d, and 1c/0b. You can cable port pairs
in the order in which they are identified (listed in the worksheet) or you can cable every other port pair (skip
port pairs).
Note: When you have more port pairs than you need to cable the stacks in your system, the best practice is
to skip port pairs to optimize the SAS ports on your system. By optimizing SAS ports, you optimize your
system's performance.
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Chapter 4 Controller-to-stack cabling worksheets and cabling examples for common multipath HA configurations