Rear backplane: 4 x 2.5-inch SAS/SATA
To connect the front backplanes, refer to “Front backplanes: 24 x 2.5-inch SAS/SATA” on page 105.
The following shows the cable connections for the 4 x 2.5-inch SAS/SATA rear backplane if installed.
From To
Backplane 4: SAS CFF expander: C3
Backplane 4: PWR Riser 1: PWR1, PWR2
Connections between connectors:  1  ↔  1 ,  2  ↔  2 ,  3  ↔  3 , ...  n  ↔  n
Figure 50. Cable routing for the 4 x 2.5-inch SAS/SATA rear backplane
106 ThinkSystem SR650 V2Maintenance Manual