This paper does a systematic review of the possible design space for cloud-hosted applications that may have\nchanging resource requirements that need to be supported through dynamic service level agreements (SLAs). The\nfundamental SLA functions are reviewed: Admission Control, Monitoring, SLA Evaluation, and SLA Enforcement ââ?¬â?? a\nclassic autonomic control cycle. This is followed by an investigation into possible application requirements and SLA\nenforcement mechanisms. We then identify five basic Load Types that a dynamic SLA system must manage: Best\nEffort, Throttled, Load Migration, Preemption and Spare Capacity. The key to meeting application SLA requirements\nunder changing surge conditions is to also manage the spare surge capacity. The use of this surge capacity could be\nmanaged by one of several identified load migration policies. A more detailed SLA architecture is presented that\ndiscusses specific SLA components. This is done in the context of the OpenStack since it is open source with a known\narchitecture. Based on this SLA architecture, a research and development plan is presented wherein fundamental\nissues are identified that need to be resolved through research and experimentation. Based on successful outcomes,\nfurther developments are considered in the plan to produce a complete, end-to-end dynamic SLA capability.\nExecuting on this plan will take significant resources and organization. The NSF Center for Cloud and Autonomic\nComputing is one possible avenue for pursuing these efforts. Given the growing importance of cloud performance\nmanagement in the wider marketplace, the cloud community would be well-served to coordinate cloud SLA\ndevelopment across organizations such as the IEEE, Open Grid Forum, and the TeleManagement Forum.
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