A system for providing a network service includes at least first and second data
centers containing the same functionality and data content. The first data center
designates a first group of resources as active, and another group of resources
as standby resources. In a similar, but reciprocal, manner, the second data center
designates a first group of resources as active, and another group of resources
as standby resources. Users coupled to the first and second data centers may access
active resources located in both the first and second data centers. In the event
of a partial or complete failure of data center resources, the standby resources
are activated and used to service user requests. In one embodiment, the data centers
include a three-tier structure including a web access tier, an application logic
tier, and a database management tier.