Capacity Planning and Power Management to Exploit Sustainable Energy
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Capacity Planning and Power Management to Exploit Sustainable Energy Daniel Gmach, Jerry Rolia, Cullen Bash, Yuan Chen, Tom Christian, Amip Shah, Ratnesh Sharma, Zhikui Wang HP Labs Palo Alto, CA, USA e-mail: {firstname.lastname}@hp.com Abstract—This paper describes an approach for designing a On the supply side, power may come from a primary power management plan that matches the supply of power power source such as the power grid, from local renewable with the demand for power in data centers. Power may come sources, and from energy storage subsystems. The supply of from the grid, from local renewable sources, and possibly from renewable power is often time-varying in a manner that energy storage subsystems. The supply of renewable power is depends on the source that provides the power, the location often time-varying in a manner that depends on the source that of power generators, and the local weather conditions. provides the power, the location of power generators, and the On the demand side, data center power consumption is weather conditions. The demand for power is mainly mainly determined by the time-varying workloads hosted in determined by the time-varying workloads hosted in the data the data center and its power management policies. We center and the power management policies implemented by the assume that the data center has pools of servers that execute data center. A case study demonstrates how our approach can be used to design a plan for realistic and complex data center consolidated workloads, and that these servers support power workloads. The study considers a data center’s deployment in management policies such as capping the amount of power two geographic locations with different supplies of power. Our used by the servers. Power may be capped if the demand for approach offers greater precision than other planning methods power from the grid exceeds the choice for available peak that do not take into account time-varying power supply and grid power. We consider two types of power capping demand and data center power management policies. policies in this work: server power capping and pool power capping. Server power capping exploits dynamic processor Keywords-component; Capacity Planning, Energy Supply frequency scaling to adjust power used by servers. Pool Management, Energy Demand Management, Power Capping power capping dynamically varies the number of running servers based on the availability of power and the demand of I. INTRODUCTION the workloads. The capping methods are complementary. Significant research is underway to develop technologies We describe a trace-driven, simulation based capacity that improve the energy efficiency of data centers and reduce planning tool that is able to simulate power management their dependence on the power grid. On the demand side, activities in data centers and estimate the impact of power virtualization technology is being used to consolidate management plans on application performance and power workloads and improve IT utilization [1]; cutting-edge usage. Traces provide the detailed information needed to: cooling technologies such as dynamic smart cooling [2] and effectively consolidate workloads onto servers; report on air-side economizers further help improve data center energy metrics that express how often demands are satisfied; and, to efficiency. On the supply side, distributed generation and estimate the impact of consolidation on workload renewable energy sources are increasingly being deployed. performance and power consumption. A chosen plan can However, the joint behavior of these technologies in an then be used during the operation of the data center to integrated supplyņdemand context is hard to predict. achieve the desired behavior. The goal of this work is to support the design of a power A case study involving three months of data for 138 SAP management plan that matches the supply of power with the applications in a real data center is used to evaluate the demand for power in data centers. We define a power effectiveness of a set of power management plans. Our management plan as a choice for the peak grid power, a mix approach gives greater precision than other methods that do of renewable energy sources, energy storage, and data center not take into account the time-varying resource usage of the server power management policies. We assume the data data center, the location specific weather data for renewable center also has a backup plan that may require the use of power sources, the time-varying supply of power, the power more grid power or diesel generators when necessary. A management policies, and the impact of energy storage sensitivity analysis using our approach can determine how technologies. often such a backup plan is expected to be employed. The paper is organized as follows. Section II gives an Although this work focuses on design time, the resulting overview of our overall approach. Section III documents the plan and its policies can be used to optimize the real time implementation of server and pool power management and management of the data center. data center energy storage in the simulator. Section IV Peak grid power usage is often a concern for data centers provides characterizations of workload demand variability as it can affect the power infrastructure of grid power and renewable power supply variability. The case study is providers. Contracts are often heavily influenced by peak presented in Section V. Related work is described in Section usage [3] and can impose penalties for exceeding an agreed VI. Section VII offers a summary and the concluding upon peak. remarks along with a description of future research. 978-1-4244-8909-1/$26.00 c 2010 IEEE 96 This paper was peer reviewed at the direction of IEEE Communications Society by subject matter experts for publication in the CNSM 2010 proceedings. Figure 1: Capacity planning to exploit sustainable energy II. APPROACH power supply traces. In our case study, we use traces of Figure 1 shows our approach for design and evaluation of measurements made every 5 minutes for sunshine (global capacity planning and power management processes. The irradiance) and wind data (average wind speed) for two first step uses historical workload demand traces and IT different locations in the US: New Mexico and Colorado. equipment descriptions to compute time-varying IT power The traces cover six weeks, three weeks of June in 1998 and demands for given data center workload on a particular IT three weeks of June in 1999. infrastructure. The time-varying IT power demands are used The global irradiance and average wind speed impact to characterize the total data center power demand assuming power supply for sources, such as PV panels or wind no constraints on power supply. turbines. To determine how much power they provide, we Next, the power supply infrastructure and its location are consider the nature of the power source (e.g., efficiency, size, selected based on the estimated power demand. This allows operational profile) and time-varying geographic data. us to use historical information to produce representative C. Simulate Power Management Plan and Report traces of power for each of the power supplies. In general, To evaluate which workloads can be consolidated to we want to consider many traces so that the impact of which servers, we employ a trace-based approach [4][5][10] representative set of behaviors can be observed for a that assesses permutations and combinations of workloads in sensitivity analysis. order to determine a near-optimal workload placement that In the third step, we simulate data center operation with provides specific qualities of service for applications. After both power supply and demand management. Various plans consolidation, the simulation based capacity planning tool can be evaluated using the tool and compared with walks forward over additional traces of workload demands to performance criteria using standardized metrics. Acceptable simulate workload placement policy. A migration controller plans are finally reported to data center designers and [8] recognizes over and under-utilized resources, causes operators to support the design of the data center and the migrations to improve application QoS, and shuts down as implementation of power management policies. well as starts up servers as needed. We have explored the The following sections describe each step in more detail. impact of various data center management policies using the A. Characterize Power Demand simulation environment [5]. The work presented in this paper We estimate each server’s power consumption within the enhances the simulation environment to implement server trace driven approach as follows. As we simulate the power capping and pool power capping policies and to take workload placement and server utilization over time, we into account the time-varying supply of power. employ the following simple linear power model: The simulator reports metrics including the CPU violation penalty for the workloads and power deficit—the , ൫ܲ௨ െܲௗ൯ difference between required and available power. Thoughכ௦௩ ൌܲௗ ݑܲ where ܲௗ is the idle power of the server and ܲ௨ is the the impact of aggressive consolidation and power deficits power consumption of the server when it’s fully utilized. The upon application performance cannot be modeled precisely term ݑ represents the CPU utilization of the server. This using the information available to us, we rely upon the CPU simple model has been shown to be a good estimator for violation penalty metric presented in [5] to estimate the power usage [3]. Other formulas could be used as well. sustained impact of resource deficits: The total IT power demand is the sum of the power per server. Finally, the power demand for the whole data center ଶ ூ ͳെݑǡ ୀଵ൫ݓǡ൯ǡݓǡ ൌͳെ ܫ ݁݊ ൌ is calculated through a Power Usage Effectiveness (PUE) ͳെݑௗǡ value [6], which is the ratio of the total power demand over ݑ and ݑ are the actual and desired CPU utilizations the IT power demand of the data center.