Cloud Computing - Cloud Data Management - page 9

From the research perspective, many researchers have proposed their definitions of
cloud computing by extending the scope of their own research domains. From the
view of service-oriented architecture, Dubrovnik [ 227 ] implied cloud computing as
“ a service-oriented architecture, reduced information technology overhead for the
end-user, greater flexibility, reduced total cost of ownership, on-demand services,
and many other things ”. Buyya et al. [ 91 ] derived the definition from clusters and
grids, acclaiming for the importance of service-level agreements (SLAs) between
the service provider and customers, describing that cloud computing is “ a type of
parallel and distributed system consisting of a collection of interconnected and
virtualized computers that are dynamically provisioned and presented as one or
more unified computing resource(s) based on SLAs ”. Armbrust et al. [ 68 ] from
Berkeley highlighted three aspects of cloud computing including illusion of infinite
computing resources available on demand, no up-front commitment, and pay-per-
use utility model, arguing that cloud computing “ consists of the service applications
delivered over the Internet along with the data center hardware and systems
software that provide those services ”. Moreover, from the industry perspective, more
definitions and excerpts by industry experts can be categorized from the perspectives
of scalability, elasticity, business models, and others [ 225 ].
It is hard to reach a singular agreement upon the definition of cloud computing,
because of not only a fair amount of skepticism and confusion caused by various
technologies, but also the prevalence of marketing hype. For that reason, National
Institute of Standards and Technology has been working on proposing a guideline
of cloud computing. The definition of cloud computing in the guideline has received
fairly wide acceptance. It is described as [ 181 ]:
“ a model for enabling convenient, on-demand network access to a shared pool of
configurable computing resources (e.g., networks, servers, storage, applications,
and services) that can be rapidly provisioned and released with minimal
management effort or service provider interaction ”
According to this definition, cloud computing has the following essential character-
istics:
1. On-demand self-service . A consumer can unilaterally provision computing
capabilities, such as server time and network storage, as needed automatically
without requiring human interaction with each service's provider.
2. Broad network access . Capabilities are available over the network and accessed
through standard mechanisms that promote use by heterogeneous thin or thick
client platforms (e.g., mobile phones, laptops, and PDAs).
3. Resource pooling . The provider's computing resources are pooled to serve
multiple consumers using a multi-tenant model, with different physical and
virtual resources dynamically assigned and reassigned according to consumer
demand. There is a sense of location independence in that the customer generally
has no control or knowledge over the exact location of the provided resources
but may be able to specify location at a higher level of abstraction (e.g., country,
state, or datacenter). Examples of resources include storage, processing, memory,
network bandwidth, virtual networks and virtual machines.