1.2.2 Ensuring availability by allocating multiple hosts with same configuration

You can allocate multiple hosts with the same configuration to use the load balancer, and to degenerate the operations just by stopping the faulty host, thereby ensuring the availability of the entire system. You can set up a Web front system with assured availability by allocation of multiple hosts with same configuration by adding duplicated hosts with the same configuration, and by allocating the load balancer, based on the single Web front system.

• Example of system setup

  The following figure shows the configuration example of a Web front system with assured availability by allocating multiple hosts with the same configuration:

  Figure 1‒4: Configuration example of Web front system with assured availability by allocating multiple hosts with the same configuration

• Tasks and their necessity

  The following table describes various tasks to be executed for setting up a Web front system with assured availability by allocating multiple hosts with same configuration and the necessity of these tasks:

  Table 1‒2: Allocating multiple hosts with same configuration and tasks to be executed when setting up the Web front system with assured availability and necessity of these tasks

  Tasks to be executed for setting up a Web front system with assured availability by allocating multiple hosts with same configuration	Necessity of executing the task	Conditions for executing the task	References
  Preparing a database	Y#	Connecting to the database	2.1.1
  Installing Application Server	Y	Mandatory (when the OS is Windows)	2.2.2
  		Mandatory (when the OS is AIX)	2.2.3
  		Mandatory (when the OS is Linux)	2.2.4
  Installing the products used for connecting to the database	Y#	For connecting to the database	2.2.5
  Setting up the system environment	Y	Mandatory	2.2.6
  Timeout settings	A	When changing to the system environment definition that fulfills the system requirements	2.2.9
  Setting and starting business applications	Y	Mandatory	2.2.10
  Settings to ensure availability	Y	Mandatory	2.3.1

  Legend:

  Y: Mandatory tasks.

  A: Tasks to be executed with the execution conditions are fulfilled.

  #: In the Example of system setup described in this manual, connection with the database is a prerequisite. Therefore, this task is mandatory.

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