Cloud Computing: Survey on Energy Efficiency <s> Processor Architecture and Design. <s> With power becoming a key design constraint, particularly in server machines, emerging architectures need to leverage reconfigurable techniques to provide an energy optimal system. The need for a single chip solution to fit all needs in a warehouse sized server is important for designers. This allows for simpler design, ease of programmability, and part reuse in all segments of the server. A reconfigurable design would allow a single chip to operate efficiently in all aspects of a server providing both single thread performance for tasks requiring it, and efficient parallel processing helping to reduce power consumption. In this paper we explore the possibility of a reconfigurable server part and discuss the benefits and open questions still surrounding these techniques. <s> BIB001 </s> Cloud Computing: Survey on Energy Efficiency <s> Processor Architecture and Design. <s> In this point-counterpoint discussion, Trevor Mudge argues for the combination of near-threshold voltage processors with techniques such as boosting to address the needs of datacenter workloads. Urs Holzle offers a cautionary note on the wisdom of giving up too much single-threaded performance to achieve energy-efficiency in large Internet service applications. <s> BIB002 </s> Cloud Computing: Survey on Energy Efficiency <s> Processor Architecture and Design. <s> In this paper we present an overview of the CoolEmAll project which addresses the important problem of data center energy efficiency. To this end, CoolEmAll aims at delivering advanced simulation, visualization and decision support tools along with open models of data center building blocks to be used in simulations. Both building blocks and the toolkit will take into account aspects that have major impact on actual energy consumption such as cooling solutions, properties of applications, and workload and resource management policies. In the paper we describe the CoolEmAll approach, its expected results and an environment for their verification. <s> BIB003 </s> Cloud Computing: Survey on Energy Efficiency <s> Processor Architecture and Design. <s> In this paper we present a concept and specification of Data Center Efficiency Building Blocks (DEBBs), which represent hardware components of a data center complemented by descriptions of their energy efficiency. Proposed building blocks contain hardware and thermodynamic models that can be applied to simulate a data center and to evaluate its energy efficiency. DEBBs are available in an open repository being built by the CoolEmAll project. In the paper we illustrate the concept by an example of DEBB defined for the RECS multi-server system including models of its power usage and thermodynamic properties. We also show how these models are affected by specific architecture of modeled hardware and differences between various classes of applications. Proposed models are verified by a comparison to measurements on a real infrastructure. Finally, we demonstrate how DEBBs are used in data center simulations. <s> BIB004
Combining different types of server components has proved promising when it comes to applying energy saving schemes. As part of the EuroCloud project,  propose a new architecture for low-power servers based on ARM processor technology. Within the CoolEmAll project BIB003 ], the prototype of the RECS system is developed and evaluated. The system, developed by the Christmann company, may include up to 18 heterogeneous computing nodes or even 72 nodes based on ARM CPUs within a single rack unit. This high density of nodes combined with fine-grained monitoring and control allows for reduced space, resources, and power consumption. Generally, solutions based on a high number of densely packed low-power processors, so-called microservers, are one of the trends visible recently on the market. In addition to physical prototype development, CoolEmAll also proposes blueprints that define efficient hardware for data centers. Furthermore, the project also defined a specification of the so-called Data Center Efficiency Building Blocks [Vor dem BIB004 ] to be used to model and simulate energy efficiency of data center components, including servers, racks, and enclosures. BIB001 propose a cluster architecture with multicore processors. The idea is to use the same processors for single-and multi-threaded operations, where a processor with four cores can be reconfigured to run only one overclocked core using power from those three that are turned off. Finally, BIB002 give an overview of challenges for choosing and building energy-efficient processors for cloud infrastructures.