Tetris and the Cloud

As discussed throughout this book, the cloud consumer views the cloud as an infinite set of resources that it can consume as required. This clearly is not the case from the provider’s point of view, nor is it a sustainable business model. So, the cloud provider (either an IT department or telco) must provide the illusion of infinite resources while continually optimizing and growing the underlying cloud platform in line with capital expenditure (CAPEX) and service-level agreement (SLA) targets. There is often debate within IT organizations as to whether a formal capacity management process is needed, as hardware costs have continued to fall. This is based on the premise that capacity management is purely a CAPEX management function; however, with the introduction of the cloud, capacity management also becomes an SLA management function. This stems from the possibility of SLA breaches because of oversubscribed equipment or lack of resources to support the bursting of existing services or the instantiation of new services, which will inversely impact the user experience of a cloud service. The self-service nature of the cloud and the increase in virtualization and automation make capacity management more complex as providers can no longer over dimension their infrastructure to support peak usage, as peak usage will vary dramatically based on consumer requirements. To visualize this, think of a typical data center as the game Tetris, as illustrated in Figure 12-1.