Grid computing is supposed to be the next major revolution in information technology after the advent of the Internet.
A Brief History of the Grid
The ancestor of the Grid is Metacomputing. This term was originated in the early eighties by NCSA Director,
Larry Smarr. The idea of Metacomputing was to interconnect supercomputer centers in order to achieve superior
processing resources. One of the first infrastructures in this
area, named Information Wide Area Year (I-WAY), was demonstrated at Supercomputing 1995. This project strongly
influenced the subsequent Grid computing activities. In fact one of the researchers who lead the project I-WAY was
Ian Foster who along with Carl Kesselman published in 1997 a paper that clearly links the Globus Toolkit ,
which is currently the heart of many Grid projects, to Metacomputing.
The Foster-Kesselman duo organized in 1997, at Argonne National Laboratory, a workshop entitled �Building a
Computational Grid� . At this moment the term �Grid� was born. The workshop was followed in 1998 by the
publication of the book �The Grid: Blueprint for a New Computing Infrastructure� by Foster and Kesselman themselves.
For these reasons they are not
only to be considered the fathers of the Grid but their book, which in the meantime was almost
entirely rewritten and re-published in 2003, is also considered the �Grid bible�.
What Is the Grid?
In 1998 Foster and Kesselman defined the Grid as follows: �A computational grid is a hardware
and software infrastructure that provides dependable, consistent, pervasive, and inexpensive access to
high-end computational capabilities.�
In fact one of the main ideas of the Grid, which also explains the origin of the word itself, was to make
computational resources available like electricity. One remarkable fact of the electric power grid
infrastructure is that when we plug an appliance into it we don�t care where the generators are located
and how they are wired. We are only interested in getting the electric power, and that�s all! Unfortunately,
in practice, the similarities between the electric power grid and the computational Grid are very few.
Actually from a computational Grid we cannot draw on computational resources, instead we have to provide
the Grid with the program to be processed along with the access to the data needed for the computation.
According to a Foster�s check list the minimum properties of a Grid system are the following:
� A Grid coordinates resources that are not subject to centralized control (e.g. resources owned by different
companies or under the control of different administrative units) and at the same time addresses the issues of
security, policy, payment, membership, and so forth that arise in these settings.
� A Grid uses standard, open, general-purpose protocols and interfaces that address such fundamental issues as
authentication, authorization, resource discovery and resource access.
� A Grid delivers nontrivial service qualities, i.e. it is able to meet complex user demands.
Therefore, a Grid should have a middleware that integrates distributed and heterogeneous computational resources
in a large, virtual computer that can be used to solve a single problem at a given time. Of course, to achieve
this result, the applications must be completely decoupled from the physical components, i.e. an application,
instead of directly accessing a physical component of the Grid, has to request it through a middleware.