ServerNet Cluster Manual

Planning for Installation
ServerNet Cluster Manual—520575-003
2-8
Planning for the Topology
Planning for the Topology
The topology you use determines the maximum size of the cluster. Table 2-2
compares the topologies.
Considerations for Choosing a Topology
•
If your cluster will contain more than 16 nodes or will grow to more than 16 nodes,
you must use the tri-star topology. The tri-star topology supports up to 24 nodes.
•
If your cluster will contain more than eight nodes but is not likely to grow beyond 16
nodes, you can build either a split-star topology or a subset of the tri-star topology
that uses two cluster switches per fabric. In this case, to chose the best topology
you need to consider:
•
Performance: A split-star topology offers twice the throughput of a tri-star
topology with two cluster switches per fabric.
•
Cable Costs: The tri-star topology with two cluster switches per fabric requires
a total of four fiber connections between cluster switches (two cables per
fabric). The split-star topology requires a total of eight fiber connections (four
cables per fabric).
•
Migration: The tri-star topology with two cluster switches per fabric provides
fast and easy migration to a full tri-star topology supporting up to 24 nodes.
Online migration from a split-star topology to a tri-star topology is more
complex and requires upgrading one fabric at a time. For more information,
refer to Section 4, Upgrading a ServerNet Cluster.
•
Software: The tri-star topology requires G06.13 (with SPRs) or a later G-series
RVU (without SPRs). The split-star topology can be constructed using G06.09
or later RVUs. (SPRs are required for G06.09 through G06.11.)
•
Features and Functions: The tri-star topology features automatic fail-over of
the two-lane links and significant defect repair. (The split-star topology also
features automatic fail-over and significant defect repair when G06.14 or
superseding SPRs are installed.)
•
If you are building a new cluster, use the split-star or tri-star topology. The star
topology is not recommended because you must change the topology to grow the
cluster beyond eight nodes.
Table 2-2. Maximum Cluster Size for Each Topology
Topology
Cluster
Switches Per
Fabric
Total Cluster
Switches
Maximum Number
of Nodes Supported
Star 1 2 8
Split-star 1 or 2 2 or 4 16
Tri-star 1, 2, or 3 2, 4, or 6 24