Planning for SAS cabling to expansion enclosures

Use these guidelines when you are installing one or more expansion enclosures.

About this task

SAS chain 1 is connected from port 1 of the node canisters in a control enclosure to the canisters in the expansion enclosures below the control enclosure.

SAS chain 2 is connected from port 2 of the node canisters in a control enclosure to the canisters in the expansion enclosures above the control enclosure.

To view an illustrated sequence of steps for installing the enclosure in a rack and beginning the setup process, see the Storwize V7000 Gen2 Installation Poster, GC27-6608.

Figure 1 illustrates how the SAS cables connect.

Figure 1. Connecting the SAS cables

Image of control and expansion enclosures that are connected by expansion enclosure attachment cables

Be aware of these guidelines when you attach the cables to the SAS ports:

Do not directly connect ports on canisters above the control enclosure with ports on those canisters below the control enclosure.
Attach cables serially between enclosures; do not skip an enclosure.
Because each control enclosure can support up to 20 expansion enclosures, it might not be possible to fit all enclosures in a single rack. Instead, install enclosures in adjacent rack space.
Each expansion enclosure is connected into the system by two SAS cables. Four different lengths of SAS cable can be used to connect expansion enclosures to a system in the same rack. Lengths longer than 0.6 m are typically required to connect between enclosures that are not adjacent in the same rack.
- 0.6 m (feature code ACUA)
- 1.5 m (feature code ACUB)
- 3.0 m (feature code ACUC)
- 6.0 m (feature code ACUD)
The last enclosure in a chain must not have cables in port 2 of canister 1 and port 2 of canister 2.
Ensure that cables are installed in an orderly way to reduce the risk of cable damage when replaceable units are removed or inserted.
Arrange your cables to provide access to the following components:
- USB ports. USB port access is required when you use a USB flash drive to configure the system.
- The enclosures themselves. Access is required to the hardware for servicing and for safely removing and replacing components by two or more people.
Ensure that each SAS cable is fully inserted. A click is heard when the cable is successfully inserted.
Note: If you make a mistake during cabling and must unplug a SAS cable, pull the blue tag to release the cable.

Table 1 lists the maximum expansion enclosures in SAS chains 1 and 2, and the available SAS cable lengths for Storwize® V7000 Gen1 and Storwize V7000 Gen2 expansion enclosures.

Table 1. Maximum expansion enclosures and cable lengths
	Storwize V7000 Gen1 (6 Gbps SAS)	Storwize V7000 Gen2 (12 Gbps SAS) 2076-524
Maximum expansion enclosures in SAS chain 1	5	10
Maximum expansion enclosures in SAS chain 2	4	10
SAS cable lengths available [meters]	1, 3, 6	0.6, 1.5, 3, 6

Storwize V7000 Gen1 expansion enclosures must not be connected to a SAS chain from a Storwize V7000 Gen2 control enclosure. However, Storwize V7000 Gen1 and Storwize V7000 Gen2 control enclosures can be clustered in a Storwize V7000 system, and all volumes will be accessible by any of the control enclosures.

SAS cables are available in 1 meter, 3 meter, and 6 meter lengths. With all components in the same rack, locating the control enclosure in the center of the rack can reduce the length requirement for the SAS cables.