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Improving Value of Capacity Planning Efforts
Proper planning and provisioning for IT services provide several key business value benefits, including providing services that meet performance and scaling expectations once they are launched.
Performing basic capacity planning tasks would make life easier for a lot of IT departments and businesses. Let’s take a look at some of the reasons capacity planning may not receive the deserved recognition or why life isn’t so easy.
Capacity planning isn’t part of the culture
Unfortunately some businesses are more concerned with meeting service levels by purchasing more hardware than needed - overprovisioning. Many IT environments are tasked with managing the day-to-day tactical operations and what planning was done was usually at a low priority.
Again, this comes down to taking a business approach and working with business managers and helping them understand how their decisions may impact service levels in the future. Making capacity planning a part of the business culture will help:
- Provision new applications accurately and efficiently
- Reduce, delay and sometimes completely avoid costs
- Justify upgrades with objective analyses
- Migrate systems to take advantage of new technology
- Reduce, delay and sometimes completely avoid costs
- Consolidate servers to simplify management and gain economies of scale
- Mitigate service delivery risk by playing out potential scenarios in advance, and then preparing for them
Corporate directives
It’s difficult to implement capacity plans when the target is always moving, sometimes drastically. By partnering with business leaders, capacity plans allow these leaders to have a greater strategic view of the impact of their decisions. A comprehensive capacity plan, when presented in business terms, can help shape the direction of business decisions.
For example, telecommunications provider CenturyTel used capacity planning to prevent a major service failure when switching customers from a legacy billing system to new billing software.
As new hardware came in, hundreds of thousands of customers at a time were being converted to the new software. A programmer kept a close watch for any potential problems, and just before one batch of customers switched, he spotted a serious problem that had evaded detection. A very significant bottleneck had fallen off the radar and no one knew about it.
Fortunately, this potential problem was corrected the day before the conversion due to solid capacity planning efforts.
Reviewing capacity planning techniques
Freeing human resources and preventing performance fires are two additional benefits of capacity planning. Capacity planning techniques include trending, simulation modeling and analytical modeling. Each technique is useful in different situations. Analytic modeling is recommended for planning and provisioning services.
Check the chart below for definitions and advantages of the different capacity planning techniques discussed in this article.
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Trending
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Trending uses simple extrapolation of resource utilization over time. The advantage of this technique is that it does not require sophisticated tools. A spreadsheet will do, but it can be difficult to take into account non-linear behavior buried deep within a multi-tiered system.
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Linear Trend Analysis
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Linear trend analysis looks at historical data and projects a linear trend line into the future, applying upper and lower confidence intervals as well as a threshold at which resources will become inadequate. This capacity planning method is a quick sanity check and identifies over-utilized resources, but it does not allow for experimentation with different configurations.
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Short Term Analysis
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Short term analysis identifies potential problems early by generating exception events (alarms) based on historical averages (rather than a fixed threshold) tied to a particular point in a periodic time interval. For example, if a particular resource averages 60% busy on Tuesdays and 50% busy on Thursdays, an exception event will only be generated when utilization crosses those thresholds on the respective days.
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Simulation Modeling
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Simulation, a much more sophisticated capacity planning technique than trending, actually simulates the queuing events that occur during execution. The downside of simulation modeling is that it can be very time-consuming to build and run the models.
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Analytic Modeling
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Analytic modeling uses mathematics to calculate how a queuing network will perform. To use analytic modeling, a baseline set of measurements is taken on a system and a model is then built based on a description of the system. Results from the model are compared with the baseline, and when they match, the model is considered calibrated. From there, hypothetical changes can be made to system configuration or business workloads, and the model will predict how the changes will affect performance. Done properly, analytic modeling is a fast and accurate capacity planning technique.
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