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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 Services (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 utilise 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
expensive option, as specialist software and hardware is required.
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Warm-Standby allows a manual switchover to take place, but with virtually no
loss of data. This is less expensive that the hot standby option as no
proprietary hardware need be purchased.
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Microsoft SQL Server also allows completely flexible online backups to take
place. For example, these can occur every few minutes if necessary.
Whilst the most manual option, this requires no extra hardware, and is
therefore also the least expensive.
Thin Client Modules
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