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Planning Volume 2, Control Workstation and Software Environment

Example 3 - An SP with 3 frames, 2 SP Switches, and various node sizes

Figure 35 shows a 3-frame system containing wide nodes, thin nodes and high nodes. The nodes have been named in accordance with their frame and slot location.

Keep in mind that you probably cannot order the system discussed in this example. This system has nodes located in legitimate locations, but the models available to order from IBM might not include this configuration. Over time, however, you might add, delete, and move nodes of your system such that you might arrive at a similar system and be faced with similar considerations.

There is an SP Switch in each of frames one and three. Frame two is sharing the first frame's SP Switch, which is possible because the configuration of frames one and two is an example of configuration number 1 in Figure 15. You can connect a maximum of 16 nodes to a switch board. Since Frames 1 and 2 have only 11 nodes total, there is room for future expansion.

Figure 35. Three SP frames with 2 SP Switches

View figure.

The nodes in a system are assigned node numbers sequentially across the frames, bottom left to top right, except that node numbers are skipped to accommodate later expansion and node shifting. Put another way, the first 16 node numbers are assigned to the 16 slots of the first frame, the next 16 node numbers to the 16 slots of the second frame, and so on. The following are cases where node numbers are skipped:

  1. A wide node takes up two slots

    For example:

  2. A high node takes up four slots

    For example:

  3. A slot is left empty

    For example:

So, how do the nodes in this system attach to the SP Switches? Each switch can have 16 nodes attached. Therefore, the system has 32 node switch ports. The system needs to know to which of these ports each node is connected. These node switch ports are numbered 0 through 31. The system understands the switch port number of a node to be the number of the node switch port to which the node is connected. The switch port number of a node is sometimes called its switch node number.

In the 16-node system of Example 1, a node's switch port number is one less than its node number, because switch port numbers start at zero. Therefore, node number 1 has switch port 0, and so on through node number 16 which has switch port number 15.

Although this discussion might sound complicated, it really isn't. Just keep in mind that a node generally sits in the midst of a large system and, at any point in time, you might care about any one of the following:

You can ascertain the current node number mapping for a system under operation by issuing the command sysparaid -i.

When possible, switch connections are made as illustrated in Example 1. Therefore, in Frame 1 of Figure 35, F1N03 sits in slot 3, is node number 3 and has switch port number 2. The wide node F1N01 is node number 1 and uses switch port number 0.

There is no node number 2, so switch port number 1 is not used by Frame 1. However, F2N01 in Frame 2 needs a switch port, and is a likely candidate to take the place of the missing node number 2 on Switch 1. So, F2N02 occupies slot 1 of Frame 2, is node number 17 in the system, and uses switch port number 1.

Continuing along this track, F1N05 uses switch port number 4 and F2N05 uses switch port 5. Switch port 6 is unused since there is no F1N07, but switch port 7 is used by F2N07.

Switch port numbers continue with the next switch of the system. So, F3N01 uses switch port 16, F3N02 uses switch port 17, and so on. However, the F3N01 is node number 33 and F3N02 is node number 34.

Now, assume you want to partition this system as follows:

             Partition 1 - F1N01, F2N01, F1N05, F2N05,
                           F1N03, F2N07
             Partition 2 - F1N09, F1N13, F2N13
                           F1N11, F2N11
             Partition 3 - F3N01, F3N02, F3N05, F3N06,
                           F3N03, F3N07,
                           F3N09, F3N13

The nodes are listed in this order on purpose - by switch chip. This layout is not among the predefined ones shipped with the SP. You can use the System Partitioning Aid to help specify this layout. First, recognize that for this system to ever have been operational, the system was installed and its specific makeup (existing frames, existing switches, node names, node types, node numbers, switch port numbers), was stored in the SDR. The System Partitioning Aid has that data to build upon. To specify the system partitioning layout you want, do one of the following:

You can plan a system partitioning layout before it is realized. This topic is discussed in Appendix A, The System Partitioning Aid - A brief tutorial.

The System Partitioning Aid will not allow you to do something inappropriate like split a switch chip among partitions; nor define a partition having extremely poor bandwidth or reliability over the switch. (See the PSSP: Administration Guide for additional information on such restrictions.) When you are satisfied, the System Partitioning Aid will save your layout information in an appropriate directory. Note that layouts are classified based on chip assignments and the maximum number of nodes which can be attached to those chips. Therefore, this layout would be saved as an 8_8_16-layout. (8+8+16 = 32 is the maximum number of nodes you can attach to 2 switches.)

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