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The Need to Comprehend Clouds:
Why We Still Can't Use Clouds Properly
Daniel Rubio Bonilla
1
, Lutz Schubert
2
, and Stefan Wesner
3
1
HLRS, University of Stuttgart,
Nobelstr. 19, 70569 Stuttgart, Germany
rubio@hlrs.de
2
IOMI, University of Ulm,
89069 Ulm, Germany
lutz.schubert@uni-ulm.de
3
KIZ, University of Ulm,
89069 Ulm, Germany
stefan.wesner@uni-ulm.de
Abstract.
Clouds have become the modern concept of utility computing - not
only over the web, but in general. As such, they are the seeming solution for all
kind of computing and storage problems, ranging from simple database servers
to high performance computing. However, clouds have specific characteristics
and hence design specifics which impact on the capability scope of the use
cases. This paper shows which subset of computing cases actually meet the
cloud paradigm and what is needed to move further applications into the cloud.
Keywords:
Cloud, Use Cases, Cloud Dwarves, Cloud Performance Criteria.
1
Introduction
The cloud concept allows reacting to system load dynamically to distribute the
services according to actual usage, thus reducing the cost of ownership and leading to
better resource utilisation. Clouds have become the modern paradigm of utility
computing. At the same time, with the rise of GPU computing and multicore
processor architecture, there is a growing belief that performance is proportional to
the number of resources. It is thus frequently assumed that clouds can implicitly
increase the performance of applications.
This assumption is however wrong for two major reasons: (a) performance is not
generally proportional to number of resources and (b) applications do not simply
change their behaviour (and thus quality criteria), just by being deployed in the cloud.
There has been an abundant discussion on scalability and performance limitations,
which shall not be repeated here (see e.g. [1]). This paper will elaborate why these
limitations apply and which effect they have on the usability of the cloud for different
application scenarios (section 2). It will give an assessment of the difficulty and
expected value of migrating use cases to the cloud and will provide a first approach
for classifying them regarding their benefits from clouds (section 3). We will show in
particular that many factors regarding the relationship between code and cloud
