having spare servers waiting to take on the work of another server if it fails.

Since a data center is often a support center for other operations, such as business logic, it represents a potential SPOF in itself. Thus, at the site level, the entire cluster may be replicated at another location, where it can be accessed in case the primary location becomes unavailable. This is typically addressed as part of an IT disaster recovery program. While previously the solution to this SPOF was physical