Architecture of Computing Systems (Lecture Notes in Computer ...

EnergySaving Cluster Roll: Power Saving System for Clusters 163
idle interconnections in the cluster [2]. Microsoft inspects the problem from a different
viewpoint and one solution proposed is to share highly efficient power supplies
among several nodes of the system, achieving significant energy savings [3].
In this context a well-known energy management technique is DVFS (Dynamic
Voltage and Frequency Scaling). DVFS entails reducing the system energy consumption
by decreasing the CPU supply voltage and the clock frequency (CPU
speed) simultaneously. This technique has a great impact on the development of
work aimed at reducing consumption in this research context [4,5,6]. The authors
in [7] present an energy-aware method in order to partition the workload and reduce
energy consumption in multiprocessor systems with support for DVS. Freeh
et al. [8] analyze the energy-time tradeoff of a wide range of applications using highperformance
cluster nodes that have several power-performance states to lowering
energy and power, so that the energy-time tradeoff can be dynamically adjusted.
In [9], the authors use economic criteria and energy to dispatch jobs to a small set
of active servers, while other servers are transitioned to a low energy state.
Alternative strategies to limit power consumption and required cooling of
HPC clusters are based on switching on and shutting down the nodes, according
to the needs of the users’ applications. An algorithm that makes load balancing
and unbalancing decisions by considering both the total load imposed on
the cluster and the power and performance implications of turning nodes off
is described in [10]. Several policies to combine dynamic voltage scaling and
turning on or off nodes to reduce the aggregate power consumption of a server
cluster during periods of reduced workload are presented in [11]. Rock-solid [12]
and PowerSaving [13] are prototype examples of this strategy which provide
little functionality or are still under development. This paper presents a new
application which follows the same strategy, but with a much more complete
functionality. In particular, our tool allows the definition of different conditions
to activate and deactivate and nodes for a full adaption to the requirements of
the system administrator and/or the end user. The tool has been designed and
implemented as a module (Roll) for Rocks R○ [14] and employs the Sun R○ Grid
Engine (SGE) [15]. A simulation of the module under real conditions shows that
its use combined with a reasonable policy deliver considerable energy savings
compared with a conventional cluster in which all nodes are permanently active.
The article is organized as follows: Section 2 presents the hardware and software
tools used in the development of the energy saving module, and Section 3
reviews its implementation. Section 4 evaluates the performance of the energy
saving module, in terms of impact on the power consumption and execution time
of the applications. Finally, Section 5 describes some future lines of work and
summarizes the conclusions.
2 Basic Hardware and Software Tools
The target hardware platform used in this work is an HPC cluster that employs
the NPACI Rocks R○ Linux distribution as operating system, equipped with a
front-end node that is responsible of the queue system and the new energy saving
module (Roll).