Power Control for Data Center Presented by Sheng Cai

Introduction Power consumption in the large data centers has become a serious problem: Firstly, the electrical and mechanical systems for supporting the power of data centers is expensive. Second, the dollars used to pay the energy bill are billions. Third, there is a limitation for power consumption of data centers. New problems with virtualized web servers: One problem is that VMs on the same physical machine will influence each other. Another problem caused by Virtual Servers is the visibility of VM power usage.

Architecture of Power Management For a data centers, there will be four levels of power management: single server, rack enclosure, power distribution unit (PDU) and entire data center, which have their own physical and contractual power limits. Many existing works on power control focus on a single server’s power consumption. Other proposed control strategies are for the rack enclosure and PDU level recently based on centralized solutions. And these solutions could not directly be used to the data center level’s power management. There are three main reasons: 1 the computing complexity; 2 the amount of communication between centralized controller and every server; 3 the delay of communication.

Virtual Machine Power Usage Measurements Power management and control needs the available method to measure the power used by the devices. In many previous works, they measured VM power usage by tracking how much hardware resource is used by VM. Then the resource usage is converted to power usage based on the power model of the resource. However, the accurate power models are difficult to build, and how to connect each resource to the VM which is using it.

Power Control Solutions There are two different ways: heuristic-based control schemes; feedback control theory solutions. In contrast to the solutions based on heuristic schemes, the control-theoretic solutions have the benefits i.e. analytic assurance of control accuracy and system stability. There are some disadvantages on the solutions based on feedback theory. One is how to build the model of systems; another is coordination of different levels’ control loops is difficult.

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