cooling infrastructures, thus the main issue is not the
current amount of data center emissions but the fact
that these emissions are raising faster than any other
carbon emission (Berral et al., 2010). Although these
improvements in hardware are crucial, we believe that
the energy consumption could also be significantly
reduced with software in over-provisioned IaaS sys-
tems. Over-provisioning is a key behaviour at smaller
sized providers, who offer services for users with oc-
casional peaks in resource demands.
Reducing the carbon footprint of European coun-
tries is also a must and expected by the European
Commission, as well as to increase the number and
size of European Cloud providers (Schubert and Jef-
fery, 2012). By federating these providers, more com-
petitive initiatives can be founded, that can be sophis-
tically managed to meet these expectations. The gen-
eral goal of the management layer in a Cloud fed-
eration is to distribute load among the participating
cloud providers, to enhance user satisfaction by fil-
tering out underperforming providers, and schedule
and execute service calls with minimized energy con-
sumption within the selected IaaS system. To achieve
this, we have already proposed an architecture called
Federated Cloud Management (FCM – as introduced
in (Kecskem
´
eti et al., 2012)). In this holistic ap-
proach a two-level brokering solution is used: a meta-
brokering component is used to direct service calls to
providers, and then a cloud-brokering component to
map these calls onto an optimized number of virtual
machines.
In this paper we target the later, cloud-brokering
layer, and we focus on the energy-aware manage-
ment of datacenters of single cloud providers special-
ized for provisioning task-based cloud applications.
In order to enable experimentation in this field, we
have developed a CloudSim-based simulation envi-
ronment. To cope with the high uncertainty and un-
predictable load present in these heterogeneous, virtu-
alized large-scale systems, we apply a Pliant system
based approach (Dombi, 2012) to the management
of these systems, which is similar to a fuzzy system
(Dombi, 1982).
Therefore the main contributions of this paper are:
(i) the development of a cloud simulation environ-
ment for task-based cloud applications, (ii) the design
of an energy-aware and Pliant-based VM scheduling
algorithm for VM management Clouds, and (iii) the
evaluation of the proposed algorithms in the extended
simulation environment with real-world traces.
The remainder of this paper is as follows: Sec-
tion 2 presents the related VM management ap-
proaches in datacenters; Section 3 introduces our ex-
tended simulation architecture; Section 4 introduces
the advanced scheduling algorithms using the Pliant
method for VM scheduling; and Section 5 describes
the evaluation methodology and the simulation re-
sults. Finally, Section 6 summarizes the main con-
tributions of the paper.
2 RELATED WORK
Regarding energy efficiency in a single cloud, Cioara
et al. (Cioara et al., 2011) introduced an energy aware
scheduling policy to consolidate power management
by using reinforcement learning techniques to restore
a service center to an energy efficient state. Feller
et al. proposed a dynamic cluster manager called
Snooze (Feller et al., 2010), which is able to dynam-
ically consolidate the workload of a heterogeneous
large-scale cluster composed of resources using vir-
tualization. In a later work (Feller et al., 2012), they
use power meters to monitor energy usage of cloud
resources, and estimate the resource usage of VMs.
Their mechanisms address VM placement, relocation
and migration by keeping VMs on as few nodes as
possible.
Cardosa et al. (Cardosa et al., 2009) presented
a novel suite of techniques for placement and power
consolidation of VMs in datacentres taking advantage
of the min-max and shares features inherent in virtu-
alization technologies, like VMware and Xen. These
features allow to specify the minimum and maximum
amount of resources that can be allocated to a VM,
and provide a shares based mechanism for the hyper-
visor to distribute spare resources among contending
VMs. Lee et al. (Lee et al., 2010) discuss service re-
quest scheduling in Clouds based on achievable prof-
its. They propose a pricing model using processor
sharing for composite services in Clouds.
Lucas-Simarro et al. (Lucas-Simarro et al., 2013)
proposed different scheduling strategies for optimal
deployment of services across multiple clouds based
on various optimization criteria. The examined
scheduling policies include budget, performance, load
balancing and other dynamic conditions, but they ne-
glected energy efficiency, which is the aim of our
work.
Regarding fuzzy approaches, Salleh et al. (Salleh
et al., 1999) have shown how to set up and use fuzzy
logic in a traditional way for dynamic task schedul-
ing in multiprocessor systems. We have already pub-
lished a paper (Dombi and Kert
´
esz, 2011) on applying
the Pliant approach to job scheduling in Grids. In this
current paper we would like to show that it is also pos-
sible to use Pliant system for scheduling, with only a
few rules. The novelty of this contribution lies in the
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