Database Reference
In-Depth Information
4.
Rapid elasticity
. Capabilities can be rapidly and elastically provisioned, in some
cases automatically, to quickly scale out and rapidly released to quickly scale in.
To the consumer, the capabilities available for provisioning often appear to be
unlimited and can be purchased in any quantity at any time.
5.
Measured Service
. Cloud systems automatically control and optimize resource
use by leveraging a metering capability at some level of abstraction appropriate
to the type of service (e.g., storage, processing, bandwidth, and active user
accounts). Resource usage can be monitored, controlled, and reported providing
transparency for both the provider and consumer of the utilized service.
2.2
Related Technologies for Cloud Computing
Cloud computing has evolved out of decades of research in different related
technologies from which it has inherited some features and functionalities such
as virtualized environments, autonomic computing, grid computing, and utility
computing. Figure
2.1
illustrates the evolution towards cloud computing in hosting
software applications [
214
]. In fact, cloud computing is often compared to the
following technologies, each of which shares certain aspects with cloud computing.
Table
2.1
provides a summary of the feature differences between those technologies
Cloud (ISP 5.0)
Dynamic, Internet-
optimized infrastructure for
hosting your applications
ASP (ISP 4.0)
Hosted (traditionally
designed) applications
on servers at the
Internet access point
Colo (ISP 3.0)
Racks for your
equipment at the
Internet access point
SaaS
Internet-based
applications and
services
ISP 2.0
Access to servers
at the Internet
access point
ISP 1.0
Provided access
to the Internet
(dial-up, ISDN,
T1, T3)
Fig. 2.1
The evolution towards cloud computing in hosting software applications
