Administration Guide

Selecting the primary and primary backup nodes

On a system with an SP switch, you can use the Eprimary command to select two nodes, one to be used as the primary node and the other to be used as the primary backup node. In systems with the SP Switch, a dependent node cannot be a primary or primary backup node. |In systems with a two-plane SP Switch2 configuration, select a |primary and a primary backup node for each switch plane. After you run the Eprimary command and until the next Estart command is run, these nodes are considered to be the oncoming primary and oncoming primary backup nodes. When the Estart command runs, the primary field is updated based on the oncoming primary field and the backup field is updated based on the oncoming backup field.

The criteria to select a new primary backup node follows:

1. First, select a node on a switch assembly other than the switch assembly to which the primary node is attached. |A p690 node can be a switch primary or primary backup node, like any |node in the system. If possible do not select, as both primary and |primary backup, two nodes that are actually LPARs within the same p690 |server.
2. Second, if no other switch assembly exists, select a node attached to a switch chip other than the one to which the primary node is attached.
3. If no other switch chip exists, select any available node on the switch chip to which the primary node is attached.

The primary and primary backup fields are updated automatically when primary node and primary backup node failures occur. Therefore, the primary and primary backup fields reflect the state of the current system.

|Consider this scenario to understand how a system with an SP Switch |determines which is a primary node and a primary backup node. Initially, the primary node and primary backup node fields are blank. In a 16-node system, the oncoming primary node field has the default value 1 and the oncoming primary backup has the default value 16.

Figure 12. Initial values

View figure.

When the Estart command is run, the node specified in the oncoming primary field becomes the primary node. The node specified in the oncoming primary backup becomes the primary backup.

Figure 13. Estart values

View figure.

If the primary backup node fails, the primary node automatically selects a replacement.

Figure 14. Backup takeover values

View figure.

If the primary node fails, the primary backup node automatically becomes the primary node and a new primary backup is selected.

Figure 15. Primary takeover values

View figure.

In summary, primary and primary backup fields reflect the current state of the system and the oncoming fields do not apply until the next time the Estart command runs.

|In a system with a two-plane SP Switch2 configuration, the previous |scenario applies similarly for each switch plane.

Using SMIT to set the oncoming primary and primary backup nodes

TYPE

smit

• The System Management menu appears.

SELECT

RS/6000 SP Systems Management

• The RS/6000 SP Systems Management menu appears.

SELECT

RS/6000 SP Cluster Management

• The RS/6000 SP Cluster Management menu appears.

SELECT

Perform Switch Operations

• The Perform Switch Operations menu appears.

SELECT

Set Primary/Primary backup Node

• The Set Primary/Primary Backup Node menu appears.

Using the command line to set the oncoming primary and primary backup nodes

On an SP Switch system for example, to select by IP address the node at 129.33.34.1 as oncoming switch primary and the node at 129.33.34.56 as oncoming switch primary backup, you can use the command:

Eprimary 129.33.34.1 -backup 129.33.34.56

|In a two-plane SP Switch2 configuration, for example, to select by |IP address the node 129.33.34.1 as oncoming switch |primary and the node 129.33.34.56 as oncoming switch |primary backup on both switch planes, you can simply allow the -p |flag to default to all or you can use the command:

|Eprimary -p all 129.33.34.1 -backup 129.33.34.56
| 

|This is an example of setting different nodes on each switch |plane:

|Eprimary -p 0 129.33.34.1 -backup 129.33.34.56
|Eprimary -p 1 129.33.35.1 -backup 129.33.35.56

See the Eprimary command in the book PSSP: Command and Technical Reference.