IBM and Pyramid are two cluster companies that also sell MPP systems, but only Pyramid allows you to include its MPP system in a cluster. While clusters give companies both increased scalability and high availability, currently most users are more interested in availability. They also value the fact that members of a cluster can be busy with processing tasks while standing ready to take over another member's work in the event of a failure. The company provides MSAT satellite communications to telecommunications carriers. The second is a hot standby connected to the first via DECsafe Available Server.
Clusters achieve their high availability through redundancy.
As soon as a member senses a failure, it takes over the jobs of the failed processors. Normally users who were logged on to the failed machine are automatically relogged into another machine, a process which may take several seconds to several minutes. Automatic fail-over is important when purchasing a cluster for high availability. MSAT, an alternative to cellular technology, provides communications via pager, fax or voice phone to users through resellers such as Bell Mobility. The server is used to activate the service for customers and to collect usage data for billing purposes.