Demand forecasting and capacity planning

This following content is a transcript from Site Reliability Engineering with some, maybe none, personal adjustments.

Demand forecasting and capacity planning can be viewed as ensuring that there is sufficient capacity and redundancy to serve projected future demand with the required availability. There’s nothing special about these concepts, except that a surprising number of services and teams don’t take the steps necessary to ensure that the required capacity is in place by the time it is needed. Capacity planning should take both organic growth (which stems from natural product adoption and usage by customers) and inorganic growth (which results from events like feature launches, marketing campaigns, or other business-driven changes) into account.

Several steps are mandatory on capacity planning:

• An accurate organic demand forecast, which extends beyond the lead time required for acquiring capacity
• An accurate incorporation of inorganic demand sources into the demand forecast
• Regular load testing of the system to correlate raw capacity (servers, disks, and so on) to service capacity

Because capacity is critical to availability, it naturally follows that the SRE team must be responsible for capacity planning, which means they also must be in charge of provisioning.