Expansion canister ports
Each Storwize® V3700 expansion canister has two SAS ports. These ports are used to connect to other Storwize V3700 enclosures.

SAS port 1 (inbound) 1 is used to connect this expansion enclosures to the Storwize V3700 control enclosure either directly or chained through other expansion enclosures. A SAS link consists of four lanes, called phys. The port is a mini-SAS HD socket. This port must be connected. SAS cables should be plugged in with the blue release tag oriented below the connector.
SAS port 2 (outbound) 2 is used to connect this expansion enclosures to further expansion enclosures in the chain. A SAS link consists of four lanes, called phys. The port is a mini-SAS HD socket. The use of this port is optional. SAS cables should be plugged in with the blue release tag oriented below the connector.
Do not connect a cable to the Service port 3 .