Intergraph WebScale User Manual page 12

WebScale™ User's Guide
Database Access within Load balanced Server Applications
Some server applications access a database that is updated by client requests. When
these applications are load balanced in the cluster, these updates need to be properly
synchronized. Each server can use independent copies of databases residing within
their individual servers, which are merged offline as necessary. Alternatively, the
clustered servers can share access to a separate, networked database server, as shown in
the diagram below. A combination of these approaches can also be used. For example,
web pages can be replicated among all clustered servers to ensure fast access and
complete fault tolerance. However, database requests should be forwarded to a shared
database server to synchronize updates from multiple web servers. Some mission-
critical applications may require the use of highly available database engines to ensure
complete fault tolerance for the service. Over the next five years, clustered database
software will be deployed to deliver highly available and scalable database access
within the cluster.
For more information on how WebScale achieves fault-tolerance and scalability, please
consult the section Theory of Operation.
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