  Recent increase in energy prices has led researchers to find better ways for
capacity provisioning in data centers to reduce energy wastage due to the
variation in workload. This paper explores the opportunity for cost saving
utilizing the flexibility from the Service Level Agreements (SLAs) and proposes
a novel approach for capacity provisioning under bounded latency requirements
of the workload. We investigate how many servers to be kept active and how much
workload to be delayed for energy saving while meeting every deadline. We
present an offline LP formulation for capacity provisioning by dynamic deferral
and give two online algorithms to determine the capacity of the data center and
the assignment of workload to servers dynamically. We prove the feasibility of
the online algorithms and show that their worst case performance are bounded by
a constant factor with respect to the offline formulation. We validate our
algorithms on a MapReduce workload by provisioning capacity on a Hadoop cluster
and show that the algorithms actually perform much better in practice compared
to the naive `follow the workload' provisioning, resulting in 20-40%
cost-savings.
