IBM eX5 Implementation Guide

236 IBM eX5 Implementation Guide

6.5.2 Processor requirements

To maximize performance, both nodes must have all four processors and all memory cards

installed and populated. However, the x3850 X5 does support 2-node configurations with only

two processors installed in each node.

The following list shows the processor requirements to perform scaling:

򐂰 Functioning processors must exist in processor sockets 1 and 4 of both servers.

򐂰 The processor specification must match among all processors in both servers.

6.5.3 Memory requirements

For scaling to be permitted, you must install the memory in such a way so as to support

Hemisphere Mode on the processors of both nodes. See Table 3-15 on page 81 to see which

memory configurations enable Hemisphere Mode.

To maximize performance, all four processors in both nodes must be in Hemisphere Mode. If

needed, the servers can be scaled with only processors 1 and 4 in Hemisphere Mode in both

nodes, but this type of configuration cannot support operating systems, such as VMware. For

other less sensitive operating environments, if the unlikely failure of a memory card takes

processor 1 or 4 out of Hemisphere Mode, you can restore the scaled environment by

swapping memory cards from processor 2 or 3.

6.5.4 Cabling the servers together

The QPI cables that are used to cable the two x3850 X5s together are extremely short and

stiff. To plug the cables in, you must start the cable insertion on both sides of the cable into

the correct receptors on both x3850 X5s at the same time.

Use the following tips when plugging in the cables:

򐂰 QPI cables ship packaged with reusable plastic boots that protect the fragile outside

edges of the cable connectors, as shown in Figure 6-12. It is a good idea to keep a set of

these plastic boots if you want to remove the QPI cables for the movement of equipment

from rack to rack or for servicing the unit.

Figure 6-12 Reusable QPI cable connector protective boot

Chapter 6. IBM System x3850 X5 and x3950 X5 237

There are four QPI cables connecting all of the QPI ports of both x3850 X5 servers.

Figure 6-13 shows the cable routing.

Figure 6-13 Cabling diagram for 2-node x3850 X5

Consider this important information:

򐂰 The QPI cables are keyed to be inserted only one way. A quick visual check for cable

orientation is to look for the blue retainer release tab on the top of each cable end. The

blue retainer release tab is placed on what becomes the visible top of the cable when the

cable is installed correctly.

򐂰 The ends of the cable are labeled to indicate which end can be inserted into the correct

equipment. The server that becomes the primary node has the end of the QPI plugged

into it with the labels J2 and J1, as shown in Figure 6-14. The secondary node has the end

of the QPI cable plugged into it with the labels J4 and J3. All four QPI cables must be

oriented in the exact same manner. Neither server can power on if the cables are not

consistent in their orientation. Figure 6-14 shows how the cable ends are labeled.

Figure 6-14 QPI cable end labels: J1 and J2 attach to the primary node

Rack rear