ServerNet Cluster 6780 Planning and Installation Guide (G06.24+, H06.03+)

ServerNet Cluster Overview
ServerNet Cluster 6780 Planning and Installation Guide—527301-004
1-6
Automatic Fail-Over
Cluster Switch Module
Within a 6780 cluster group, each 6780 switch module represents one 6780 switch.
Each module is numbered one through four from bottom to top. The switch module
number and switch layer number are always the same.
Cluster Switch Name
The cluster switch name consists of the fabric, zone, and layer. For example, the 6780
switch on the X fabric, zone 2, and layer 1 is named X21.
Automatic Fail-Over
Clusters support automatic fail-over of ServerNet traffic between zones, but not
between layers. With fail-over, internode paths stay up on both fabrics as long as at
least one connection between the 6780 switches is functional.
If a connection is repaired, it is automatically brought online again after it has passed
neighbor checks.
Message-System Traffic and Expand
In a ServerNet cluster, message-system traffic flows directly between processors by
way of the message system but under the control of Expand. Figure 1-2 diagrams the
traffic.
Secure message-system traffic between processes on different ServerNet nodes
travels through the Expand-over-ServerNet line handlers, and through the local
message system between the communicating processes and the line handlers.
Nonsecure message-system traffic flows directly between processors through the inter-
system message-system ServerNet connections as directed by the Network Routing
Table (NRT) under the control of Expand. The intersystem ServerNet message-system
connections are not used if the appropriate settings are not made in the NRT.