3.. Optimize.the.HA-module: Configure the HA-module so that only write operations
are multicast with strict ordering to whole replica set. These actions would be limited
to profile updates and personal messages. With this simple configuration, read operations,
which are clearly dominant in this example, will show a performance similar
to the non-replicated Web application.
4.. Enhance. availability. of. consistency-relaxable. actions: In our example, a set of
statistics such as pages viewed, preferred profiles, or visits received could be examples
of data that do not need strict consistency, and most cases allow some amount of data
loses. A simple way to enhance their availability without the need of synchronous
ordered multicasts could be to create a Web service to be requested automatically, let
us say, at night, to read each replica data, updating all of them with cumulative data.
To this end, ordinary page requests would be fast, and just those URLs requested
during the global updating phase would be configured as write operations into the
HA-module.
With these quite simple steps, a fairly complex Web application could be made highly available.
Finally, one additional step that should be analyzed is replica distribution.
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