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. Introduction
. Design
Goals
. Logical
Architecture
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Physical Architecture
. Conclusion
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Thick Client Modules
There are up to three physical layers for an installation
of Land, Build or Care:
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Many client computers, each running Windows 2000 Professional or Windows XP
Professional.
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One or more business rules servers, running Windows 2000 Server.
Microsoft Component (COM+) provides the technology to host the
business rules components on the server.
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One database server, running Windows 2000 Server, and SQL Server 7 or 2000.
If there is only one business rules server (where only a small number of
clients are required), then it is possible for the business rules and database
server to be the same physical machine.
Scalability
The performance of database servers is increased by expanding a single server - for example, adding more processors or memory. For business rules servers, however, scalability is achieved by clustering many separate servers together, and then using load-balancing techniques to utilize all the machines as fully as possible.
Availability
Availability is primarily concerned with removing any single points of failure. If there are multiple business rules servers in a load-balanced configuration, then other machines in the group will take over if one fails.
Database servers are made highly available by:
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Hot-Standby technologies allow an identical server to immediately and automatically take over if the primary server fails. This is the most failsafe option but requires specialist software and hardware.
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Warm-Standby allows a manual switchover to take place, but with virtually no loss of data. This is less expensive than the hot standby option as no proprietary hardware need be purchased.
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Microsoft SQL Server also allows completely flexible on-line backups to take place. For example, these can occur every few minutes if necessary. While the most manual option, this requires no extra hardware, and is therefore also the least expensive.
Thin Client Modules
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