Introduction to Analytical Modeling.
Gregory V. Caliri · 2000
Analytical models are constructed and used by capacity planners to predict computing resource requirements related to workload behavior, content, and volume changes, and to measure effects of hardware and software changes. Developing the analytical model provides the capacity planner with an opportunity to study and understand the various behavior patterns of work and hardware that currently exist. Certain factors must be taken into consideration to avoid common errors in model construction, analysis, and predictions. Definition of Analytical Modeling What is an analytical model? By pure definition and in terms of being applied to computer systems, it is a set of equations describing the performance of a computer system. In practical terms, it describes a collection of measured and calculated behaviors of different elements over a finite period of time within the computer system – workloads, hardware, software, and the CPU itself, and can even include the actions and behaviors of its users and support personnel. In most instances, the capacity planner constructs the model using activity measurement information generated and collected during one or more time intervals. It is critical that an interval or series of intervals be used that contain significant volumes of business-critical activity. Units of work are then characterized by type and grouped into workloads. The capacity analyst can then translate future business requirements into measurable units of computing resource consumption, and calculate capacity and performance projections for workloads. Purposes for building Analytical models Some users will construct analytical models to merely gain an understanding of the current activity on the system and to measure performance and analyze behavior of the workloads and hardware within it. Others will use them as a basis for prediction of behavior of certain elements of work within a system by inputting changes to different components of the system; one might include changes to faster or slower hardware, configuration changes, increased or decreased or altered workload arrival patterns. changes. Some will even carry the use of an analytical model beyond entering changes to the current system or set of systems and use it as input to a second model so as to measure the effects of the combination of two existing systems. For most sites, the projection of capacity requirements and future performance are the objectives behind the capacity planning effort. In these what-if analysis situations, the capacity planner follows a several step process consisting of the following steps: Receives projections for future business computing requirements Translates those business requirements into data processing resource requirements based on the information contained in the model, and other sources, if the model does not contain sufficient workloads with characteristics meeting those requirements Calculates the status of the system after the new workload requirements have been input Reports results to management, listing any available options.