Distribute Members When you deploy a fault-tolerant program, it is important to distribute the member processes appropriately across both computers and network segments. Independence increases the effectiveness of redundant processes. Protect against Hardware Failure To protect a fault-tolerant program against hardware-related failures, each member process must run on a separate computer. If two members were to run on the same computer, then both processes would be vulnerable to exactly the same failures; a single disconnected power cord or loose network cable would disable both processes simultaneously. Consider redundancy of special hardware. For example, if the program relies on a data feed line, install one line on each computer that runs a member process. If the program relies on a special board or card, install that hardware on each computer that runs a member process. Protect against Network Disconnect If the program serves a network consisting of several segments, distribute member processes appropriately across all the segments. To protect against disconnect from the rest of the network, run at least one member on each segment. Consider using redundant copies of software and data files. If all the members of a group depend on network access to a single data file, then network disconnect would disable all the processes that can no longer access that file.
