Maintenance involving planned outages
Load Balancer: Incompatible upgrades
We refer to upgrades as incompatible if an updated Load Balancer cannot exist in a High Availability configuration with a not -yet-updated Load Balancer. Possible reasons for incompatibility include:
- Installation of a new major release with an incompatible High Availability mechanism
- Migration to a new solution (for example, different software or a hardware-based solution)
- Migration to a different High Availability solution (for example, TSA)
- Migration to a new operating system.
In the case of an incompatible upgrade, IBM recommends installing the new high available load balancing configuration in parallel to the current installation, on new, dedicated hardware.
If you can use dedicated hardware, you need to make sure that no IP traffic is routed to the new installation during the setup phase, for example, by using different IP addresses or a separate network. When the installation is done, take down your current Load Balancer hardware and switch over to using the correct IP addresses on the new hardware.
If you want to reuse your existing hardware, you need to stop load balancing before installing the new solution. If you have a Web server that can handle the traffic for your site during the time frame for setting up the Load Balancer, you can temporarily assign the Web server cluster IP address to that Web server. Otherwise, IBM recommends taking the site down by having one Web server display a maintenance page (see 27.2.4, Maintenance Web page for site downtimes) and temporarily assigning the cluster IP address to that Web server.
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