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Cloud, there are differences in the typical usage pattern. Grid is typically used for
job execution, e.g. the execution of a HPC programme for a limited time. Clouds
do support a job usage pattern but are more frequently used to support long-running
services (EGEE 2008).
While most authors acknowledge similarities among those two paradigms, the
opinions seem to cluster around the statement that Cloud Computing has evolved
from Grid Computing and that Grid Computing is the foundation for Cloud
Computing. Foster et al. (2008) for example describe the relationship between Grid
and Cloud Computing as follows:
“We argue that Cloud Computing not only overlaps with Grid Computing, it is
indeed evolved out of Grid Computing and relies on Grid Computing as its backbone
and infrastructure support. The evolution has been a result of a shift in focus from an
infrastructure that delivers storage and compute resources (such is the case in Grids) to
one that is economy based aiming to deliver more abstract resources and services (such is
the case in Clouds).”
Thus, Cloud and Grid computing can be considered as complementary. Grid inter-
faces and protocols can enable the interoperability between resources of Cloud
infrastructure providers and/or a Federation of Clouds. Grid solutions for job
computing can run as a service on top of a Federation of Clouds and/or a distrib-
uted virtualized infrastructure (Llorente 2008a, Llorente 2008b). In addition, the
potential benefits of simplicity offered by Cloud technologies, such as higher-level
of abstractions (Jha et al. 2008), may help to better serve current Grid users, “attract
new user communities, accelerate grid adoption and importantly reduce operations
costs” (EGEE 2008).
In the discussion about the differences among Grids and Clouds, less attention is
given to explaining them from user perspective yet. Based on the described features
of Grid Computing in chapter 3 and Cloud Computing in this chapter, the main
changes from the user perspective can be summarized as follows:
•
Pure focus on X-as-a-Service (XaaS) by Clouds
: As mentioned in section 3.2 in
chapter 3, the basis for Grid Computing is Grid middleware that is available on
the market as packaged or open source software. Utility Computing is only one
form of Grid Computing. Compared to that, Cloud Computing focuses purely
on XaaS offered in a pay-per-use manner. There is no middleware that enables
the building of Clouds yet.
•
Focus on different types of applications:
Grid Computing emerged in eScience to
solve scientific problems requiring HPC. Current usage in industry also focuses
mainly on HPC, for example in collaborative engineering based on simulation,
in research and development in pharmaceutical companies and similar. HPC
applications are usually batch-oriented and require high computing power for
one task that is run once in a time. Given this, Grid Computing has the goal
to assign computing resources, in many cases from different domains, to such
HPC tasks. Cloud Computing is rather oriented towards applications that run
permanently (e.g. the well-known CRM SaaS Salesforce.com) and have varying
demand for physical resources while running. In order to be more flexible, one
