A WebTrends software client once asked me if there was a general guideline for the number of analysis servers that should be used as the number of profiles increases. In other words: “How many profiles can we have per analysis server?” WebTrends doesn’t have an official guideline and there’s no one-size-fits-all solution, but here are some pointers.
First, we need to know whether the existing analysis servers are capable of analyzing all the jobs in a timely manner. Given enough time, one analysis server will be enough to process all the profiles in the system; but will it be able to do it at a fast enough rate for the business? Keep in mind that if the jobs are not analyzing at a fast enough rate (you’ll know this is happening when analysis queues for the day spill over to the next), then it may make the most sense to add additional analysis servers.
To help you determine how successful you are in the end, you should keep track of current performance (i.e. when do jobs typically finish analyzing on a normal weekday), and then set a goal of when all tasks should finish analyzing per day. To assess current analysis server performance, devise a way to come up with an “average profile analysis time” based on analysis timestamps for a good sample of profiles. You can then use this number as a benchmark to compare with any improvements that you may observe if you do add analysis servers.
Analysis servers could be configured to process more than one concurrent job, depending on their technical specifications. The rule of thumb is to start off with one concurrent task, then add an additional one for every 2GB past 4GB of RAM in the analysis server. For example, one concurrent task for a server with 5GB RAM or less, two for 6GB, three for 8GB. Try to limit yourself to one concurrent task less than the total number of CPU cores in the system (i.e. four CPU cores should be limited to three concurrent tasks). Note that these guidelines are for an optimal configuration; you may be able to squeeze out an additional concurrent task or two, but make sure you do some load testing before marking the installation as complete.