Many organizations operate IT in firefighting mode, reacting to performance incidents when they occur. It is surprisingly less often that organizations perform capacity planning up front, though that would ensure that systems will provide necessary service levels without interruption. Being reactive is more expensive, but nonetheless, more common than being proactive. Maybe it's human nature. It seems that few organizations possess the maturity to see the value of formally addressing capacity issues in an organized manner.
Maybe that's changing.
A recent Network World article, "10 best IT jobs right now," predicts that "Capacity Manager" will be an up and coming job title in 2010. In the article Denise Dubie suggests that tough economic conditions combined with added complexity from virtualization should help influence companies to pay more attention to capacity planning. Evelyn Hubbert of Forrester and Cameron Haight of Gartner are both quoted as emphasizing the strategic importance of capacity management for organizations seeking to maximize the value provided to a business by its IT organization.
At TeamQuest we've got tools for both proactive and reactive performance management, but we always try to influence customers to take a more proactive, service point of view. We suggest that the organizations with the highest level of capacity management maturity analyze IT capacity in terms of the business value that it can bring to an organization. (See the recent post here on the TeamQuest Capacity Management Maturity Model).