Connecting the optional 5U SAS expansion enclosures

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After you install the 5U SAS expansion enclosures into the rack, you must connect them to each 2145-SV1 or 2145-DH8 node in the I/O group that will use them.

Before you begin

Important: To support the 5U expansion enclosure, 2145-SV1 and 2145-DH8 systems require software version 7.8.0. Do not connect the expansion enclosure if software version 7.8.0 is not installed on the system.

About this task

This task applies if you are installing a 5U expansion enclosure. When you insert the SAS cables, ensure that the connector is oriented correctly to the node and expansion enclosure.
  • For 2145-24F or 2145-12F expansion enclosures, the blue pull tab must be below the cable ( 1  in Figure 1).
    Figure 1. SAS cable connector orientation
    SAS cable connector orientation
  • For 2145-SV1 or 2145-DH8 nodes and 5U expansion enclosures, the blue pull tab must be above the connector ( 2  in Figure 1).
  • Insert the connector gently until it clicks into place. If you feel resistance, the connector is probably oriented the wrong way. Do not force it.
    Note: It might be hard to attach the SAS cable to a SAS port on a 2145-SV1 enclosure. If it will not close by itself, you might need to push the SAS cable latch down with your finger (Figure 2).
    Figure 2. Pushing the SAS cable latch closed
    Pushing the SAS cable latch closed
  • When inserted correctly, the connector can be removed only by pulling the tab.

Be aware of the following guidelines when you attach the cables to the SAS ports.

  • No cable can be connected between a port on a left canister and a port on a right canister of the expansion enclosures.
  • Ensure that cables are installed in an orderly way to reduce the risk of cable damage when replaceable units are removed or inserted.
  • SAS cables must be routed through the cable management arms to reduce the risk of disconnecting the nodes from their storage arrays. This step also helps to protect the SAS cables from getting damaged if you slide the node or enclosure out of the rack while they are attached. Arrange your cables to provide access to the following components:
    • Ethernet ports, including the technician port. The technician port is used for initial setup of the system by directly attaching to a personal computer. It can also be used to complete service actions for the system.
    • USB ports. USB ports can be used to initialize the system or to perform service-related tasks by using a USB flash drive that contains executable files for initializing the system.
    • Fibre Channel and Fibre Channel over Ethernet (FCoE) ports. If your system has an optionally installed Fibre Channel and FCoE adapter for host and external storage attachment, ensure that these ports are accessible.
    • The nodes and the enclosures themselves. Access is required to the hardware for servicing and for safely removing and replacing components by using two or more people.

Procedure

  1. Install the cables, as shown in Figure 3.
    Note: Figure 3 is provided to show the cable connections between the SAS enclosures and each node enclosure. It does not imply or represent the precise racking order for the enclosures in a rack. However, due to its size and weight, always place the 5U expansion enclosure near the bottom of the rack.
    Figure 3. Connecting the SAS cables
    Example cabling between a node and expansion enclosures
  2. If more I/O groups are configured, repeat the cabling procedure for the other I/O groups. Each system can have a maximum of four I/O groups, with two chains of expansion enclosures attached to each I/O group. On each SAS chain, the systems can support up to a SAS chain weight of 10.

Combining 2U and 5U expansion enclosures

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About this task

As Figure 3 shows, you can combine 2U expansion enclosures (12 drive and 24 drive) and 5U expansion enclosures in a SAS chain. The limiting factor is the combined chain weight of the various components. The maximum SAS chain weight that can be attached to a node SAS port is 10:
  • 5U expansion enclosures have a chain weight of 2.5
  • 2U expansion enclosures have a chain weight of 1.

Example

Table 1 shows examples of different combinations of SAS weights.

Table 1. Examples of supported SAS chain combinations
Enclosures (12 drives) 2U Enclosures (24 drives) 5U Enclosures Combined chain weight
0 0 4 10
2 0 3 9.5
2 3 2 10
0 7 1 9.5
1 1 1 4.5

(as shown in Figure 3)

In addition, the orientation of the Input and Output SAS ports on the 2U and 5U SAS expanssion enclosures differs. Figure 4 shows the SAS ports on the 5U and 2U SAS expansion enclosures.

Figure 4. SAS port orientation on expansion enclosures
SAS port orientation
  •  1  Input SAS port
  •  2  Output SAS port