If you have a robust external storage system such as a
SAN (more on SANs in Chapter 10), you could do geo-clustering, which would protect
you in environmental disaster situations.
So does clustering have any value? Of course it does, especially for low-priority systems.
Businesses often prefer to select economical hardware for such systems, and
economical hardware is more prone to failure than higher priced, more reliable server
platforms. All it takes is for one cable to short out, a power fluctuation, or a failed cooling
fan to damage a single node. Clustering plays a critical role in disaster mitigation,
but just one role.
Here??™s how clustering fits in with the disaster recovery categories:
??? Environmental: Clustering is of almost no use in the event of an environmental
failure, because the servers must have direct contact (and thus close proximity) to
the shared disk. The only possible use for clusters as insurance against environmental
disaster would be in a SAN environment, in which there can be some
physical separation between the cluster nodes and the shared disk.
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