Onboard connectors
The following shows the cable connections for the 8 x 2.5-inch SAS/SATA + 8 x 2.5-inch NVMe configuration 
with onboard connectors.
From To
Backplane 1: SAS Onboard: SATA 0, SATA 1
Backplane 2: NVMe 0-1, 2-3
Onboard: PCIe 1, PCIe 2
Backplane 2: NVMe 4-5, 6-7
Onboard: PCIe 3, PCIe 4
Connections between connectors: 
1  ↔  1 ,  2  ↔  2 ,  3  ↔  3 , ...  n  ↔  n
Figure 58. SAS/SATA cable routing
Figure 59. NVMe cable routing
116 ThinkSystem SR650 V2Maintenance Manual