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Overview
Let us start this section by stating what (manual) cold swap failover setup for RapidMiner Server can actually achieve. As the name implies, cold swap failover describes a setup where the backup server is not running all the time, but rather is only started on demand, i.e. when the primary instance goes down for any reason. The outage detection and the start of the backup can either be done manually or automatically by some mechanism, e.g. a script. Please refer to the general setup documentation for detailed descriptions of the actual setup as well as information of other potential points of failure in a high availability setup.
Basic Example
In the most basic scenario, one primary RapidMiner Server instance will be running. This instance will serve all requests from Studio, as well as offer the web UI and potentially web services. Another RapidMiner Server instance will be located on a different machine, but will not be running. If the primary instance goes down for any reason, the backup instance will be started. This backup points to the same database, thus allowing a pretty much seamless transition for Studio users connected to the server as well as for web services offered by the server. See the How-to section for detailed information on how to automate both the detection and the swap.
Downtime
Given the fact that the backup server will only be started after the primary server goes down, there will be a short period of time where no server is active to serve requests. The length of this downtime is determined by the time passing between the primary server going down and the backup server being ready as well as a load-balancer pointing to the backup server. Starting RapidMiner Server takes about twenty to thirty seconds out of the box on a standard machine, so on average the downtime when a cold swap becomes necessary should be less than one minute. Exact values obviously vary depending on given hardware, exact outage detection mechanism, failover technology, and the overall setup and circumstances. For more details on limitations of cold swap failover, please refer to the section about limitations.
