High Availability Guide : Watchdog sample : HotStandby configuration using Watchdog : System design issues
  
System design issues
How you configure HotStandby (locally or remotely, at one or more different locations, over the Internet, and with the Watchdog program) can affect the reliability and efficiency of your system. This section addresses these issues.
The illustration below shows one example of a heterogeneous system, in which the Primary and Secondary servers do not even use the same type of hardware and operating system.
See also
HotStandby configuration using Watchdog