posted 08-01-2002 02:09 AM         

Ive been invloved in both of these before.

Capacity Planning is future planning for projected user levels/throughput/capacity of you application(s)/system(s)/harware.

Now this can be theoretical, based simply on statistics you may have gathered from your production environment and maybe using modelling tools or ideally utilizes load testing to more accurately anticipate maximum/optimal capacity of your applications, systems and hardware.

When I've been involved in this in the past we ran load tests to as closely as possible mimick a real user on a 1:1 ratio and the support team made changes to configurations and hardware to see what effects this would have if introduced into the production environment. I did have an advantage here though in that we had an identical setup in our test environment to the production environment which not every body can do!

Just my tuppence worth, im sure others will ellaborate further on their experiences.

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Hope this helps.

Regards,
Colin.

posted 08-01-2002 09:53 PM         

Performance analysis must have a reason and a goal.

Capacity planning is one of the reasons and the goal here, as Colin put it, is to predict hardware and software capacities of applications and systems. The reason is the business need to invest accordingly in advance.

Load Testing is one method used to assess capacity. And can be classified under the heading of measurement. You conduct experiments under a model that you create, measure and finally extrapolate the results if needed.

The other methods I can think of are simulation and analytical modeling. A simulation is a programmatic mock-up of the final system. This may involve the use of parts / components that the final system will comprise of. This can be used in the post-design phase itself. Analytical modeling is a technique that is solely based on the usage of queuing theory on the final system, albeit on paper.

To summarize, capacity planning is an activity and load testing is a method. We could do capacity planning using load testing, among others.