Deploy new static content | Quiescing a Web server
Maintenance involving planned outages
Upgrades to the Web server tier may not always be possible without stopping one or more Web servers for some time. After explaining a technique called quisling for gracefully removing a Web server from the Load Balancer cluster (see 27.2.1, Quiescing a Web server), we look at different types of upgrades requiring server outage:
- Compatible upgrades, where an updated Web server can be restarted while non-updated Web servers are still online (See 27.2.2, Compatible upgrades.)
- Incompatible upgrades, where updated Web servers must not be restarted while any non-updated Web servers are still online (See 27.2.3, Incompatible upgrades.)
In both cases, not all the servers need to be stopped at the same time when following our instructions. The WebSphere Commerce site can be kept online.
While in many cases our High Availability configuration allows us to keep the WebSphere Commerce site online, there might still be upgrades (typically at the application and database tiers) that require taking the entire site down. We describe how to configure the Web servers to display a maintenance page before making these kinds of updates (see 27.2.4, Maintenance Web page for site downtimes).
Important: When performing the upgrades described in the following sections, one or more of your Web servers are down for a certain amount of time. To ensure that the remaining Web servers can still handle the incoming requests without performance degradation, utilization of each Web server should not be more than 50% (CPU, memory, open files, sockets, and so on) at peak times when all Web servers are online. If this is not the case, consider performing upgrades at off-peak times or temporarily adding more Web servers.