TABLE OF CONTENTS The operation of a Web hosting facility involves control elements and decisions spanning many time scales. The physical computing facility contains many control points with parameters that can be tuned in real time to respond to performance statistics. At one extreme, high-performance routers operate at very fine time scales and adjust their parameters accordingly. Operating system, middleware, and application software may also monitor performance and set control parameters. At somewhat coarser time scales, computer and disk farm partitions may be reassigned in response to changing workloads. Daily, weekly, monthly, and longer term forecasts may be used to schedule and plan allocation policies. At weekly and monthly time scales, the capacity of the resource elements may be reviewed and cause a utility's supply chain model to process additional orders or to obtain short-term capacity. Finally, monthly and yearly performance reporting may require changes in the basic terms and conditions of the service level agreement (SLA) and impact strategic models addressing a computing utility's profitability. The key operational point is that the overall solution must provide a unified framework that makes it possible to have various solution methods working together in a cohesive manner across a wide range of time scales in order to meet a common overall goal.
The physical computing facility includes control points at the router and server. Policies at these control points can be used to achieve quality of service (QoS) performance objectives through the allocation of resource elements, once...
