N+1 Clustering
As clustering is used more widely within an organisation, "N+1" clustering becomes an attractive means to reduce the cost overhead associated with the technology.
With this approach, a larger number of active servers are all grouped with a single fail-over server able to take over from any one of them in the event of a server failure. If there are three servers that require protection, as in the example below, the cost overhead is reduced from 100% to only 33%.
N+1 Clustering
Advantages
- Reduced cost overhead - As per the example above.
- Reduced management cost - Fewer, larger clusters to manage means lower total cost of ownership.
Disadvantages
- Greater complexity - The architecture is clearly more complex than basic two-way fail-over, though modern enterprise clustering software largely addresses this issue.
Organisations that also require protection against an entire site outage or disaster, are increasingly choosing to deploy the ultimate in high availability solutions - multi-site clusters.
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