Administration Guide

Understanding the switch and the types supported

A switch provides a means for nodes to communicate with each other faster and more efficiently. For example, a switch can dramatically speed up TCP/IP, file transfers, remote procedure calls, and relational database functions. A switch consists of a switch assembly and the internal cables to support connections to the processor nodes. A switch can provide some or all, depending upon the type of switch, of the following capabilities:

• Interframe connectivity and communication
• Scalability for increased number of nodes including intermediate switch frames
• Constant bandwidth and latency between node pairs
• Support for Internet Protocol (IP) communication between nodes
• IP Address Resolution Protocol (ARP) support
• Support for dedicated or multi-user environments
• Error detection and retry
• Fault isolation
• Concurrent maintenance for nodes

|Switches provide enhanced scalable high performance communication |between processor nodes, most especially for parallel job execution. |The following switches are supported with PSSP 3.4: |

• |SP Switch |
  • |This switch connects all the processor nodes in the system.
  • |You can use an SP Switch with 16 ports in a tall SP frame for SP systems |with or without SP-attached servers and in systems of clustered enterprise |servers that are running the PSSP software.
  • |You can use an SP Switch with 8 ports for smaller SP systems with up to |eight processor nodes in short SP frames.
  • |There are frame, switch, and node placement and numbering rules and there |are switch port numbering rules to be understood and honored for the supported |switch capsule configurations. |
• |SP Switch2 |
  • |The SP Switch2 supports two different switch configurations so that nodes |can communicate over one or two switch planes. You can have improved |communication performance with two switch planes operational, and higher |availability since one switch plane can continue operating even when you take |a switch down for maintenance.
  • |A two-plane SP Switch2 system has two sets of switches and two |switch adapters per node. The switch planes are disjoint - each |is cabled exactly like a single plane, both with the same topology, and |communication across the pair of planes is achieved by a data striping |algorithm in the software. You can only use this option with nodes that |can have two adapters - one for connecting to one switch plane and |another for connecting to the other switch plane. You cannot install |one adapter in some nodes and two adapters in others.
  • |With the control workstation and all the nodes running the PSSP 3.4 |software, you have optional switch connectivity. This means a system |using the SP Switch2 can have some nodes that are not connected to the |switch. This way you can use the SP Switch2 and still keep older nodes |in your system, but not connected to the switch if they are not supported on |the SP Switch2.
  • |The SP Switch2 can still be configured with one switch plane. Then |it is like the SP Switch with one adapter per node that is attached to the |switch network and one switch plane. But it also has the added |functional benefits, like relaxed node placement rules and optional |connectivity. |
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See the book IBM RS/6000 SP: Planning Volume 2, Control Workstation and Software Environment for more discussion of the supported switch configurations and rules or for the list of nodes that can connect to these switches.

Note:

Throughout this book use of the term SP switch (with the lower-case s in switch) applies generically to both the 8-port and 16-port SP Switch and to the SP Switch2. Exceptions are explicitly noted where applicable, like in discussions of system partitioning and clocking.