Grid Computing - Guide to Cloud Computing for Business and Technology Managers - page 251

12.6 Grid Technologies
First of all, grid computing defines a notion of a virtual organizations to enable
flexible, coordinated, secure resource sharing among participating entities. A
virtual organizations (VO) is basically a dynamic collection of individuals
or institutions from multiple administrative domains. A VO forms a basic
unit for enabling access to shared resources with specific resource-sharing
policies applicable for users from a particular VO. The key technical problem
addressed by grid technologies is to enable resource sharing among mutu-
ally distrustful participants of a VO who may have varying degrees of prior
relationship (perhaps none at all) and enable them to solve a common task.
The five layers of grid computing are interrelated and depend on each
other. Each subsequent layer uses the interfaces of the underlying layer.
Together, they create the grid middleware and provide a comprehensive
set of functionalities necessary for enabling secure, reliable, and efficient
sharing of resources (computers, data) among independent entities. This
functionality includes low-level services such as security, information,
directory, resource management (resource trading, resource allocation,
quality of service), and high-level services/tools for application develop-
ment, resource management, and scheduling. In addition, there is a need
to provide the functionality for brokerage of resources and accounting and
billing purposes.
The main functionalities of a grid middleware are
• Virtualization and integration of heterogeneous autonomous
resources
• Provision of information about resources and their availability
• Flexible and dynamic resource allocation and management
• Brokerage of resources either based on company policies
• Security and trust (Security includes authentication [assertion and
confirmation of the identity of a user] and authorization [check
of rights to access certain services or data] of users as well as
accountability.)
• Management of licenses
• Billing and payment
• Delivery of nontrivial Quality of Service (QoS)
An extensible and open grid architecture shown in Figure 12.1 was defined
by Ian Forster in The Anatomy of the Grid in which protocols, services, appli-
cation programming interfaces (APIs), and system development kits (SDKs)
are categorized according to their roles in enabling resource sharing.