This equivalence is clearly required since only one node of the cluster is used at
any point for the entire workload. If one node fails, the other should be capable of
running the same workload with equal performance.
With Real Application Clusters, you can use both nodes of the cluster concurrently
to spread the workload, reducing the load on one machine or node. You must still
make sure that each machine will be powerful enough to adequately handle the
entire workload (albeit at a reduced performance level) to meet basic business
requirements when a node is not available.
Of course, using Real Application Clusters to spread the workload over several
machines will result in a lower percentage of each machine??™s resources being used in
normal operating conditions, typically more expensive than using fully utilized
machines. Each machine in the cluster must devote some overhead to maintaining its
role in the cluster, although this overhead is minimal. You will have to weigh the
benefits of carrying on with some performance degradation in the event of a node
failure versus the cost of buying more nodes or more powerful machines.
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