|
|
We have discussed various techniques to implement high availability end-to-end WebSphere production systems. Availability commonly refers to uptime. Using techniques discussed here, you can build the entire WebSphere system with 99.5% availability or better.
High availability is not only for 7x24 businesses. There are two types of downtimes: planned downtime and unplanned downtimes. The techniques we discussed are for both planned downtime and unplanned downtime. Clustering techniques make rolling upgrades of hardware and software and hot replacement possible. Nobody knows when unplanned downtime will occur. It might occur during your business hours, even though you are in a 5x8 business. Clustering techniques help the system with automatic fault detection and service recovery. If you want to avoid interruptions to your operations due to system failures, then use these techniques whether you are a 7x24, 6x20, or 5x8 business. Non-7x24 business hours provide opportunities for planned downtime for system maintenance and software/hardware upgrades off-line, but your system can still fail at any time due to hardware, software, and network problems.
Any high availability implementation needs high investment in hardware, software, and skilled personnel. Therefore, it is important to evaluate how much you will lose if your system is down during your operation hours.
WebSphere production system availability is determined by the weakest link in the WebSphere system chain. Therefore, it is very important to evaluate each part of the end-to-end WebSphere system high availability and eliminate all single points of failure, as shown in Figure 15-23.
Figure 15-23 An end-to-end WebSphere system that removes single points of failure
