A PHYSICAL VIEW

1. Prof. Neeraj Bhargava
Pooja Dixit
Department of Computer Science
School of Engineering & System Sciences
MDS, University Ajmer, Rajasthan, India
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2. A grid is a collection of networks, processors, storage,
and other resources.
 Networks The networking mechanism is the most
fundamental resource for the grid and also is the
theme of this book.
 In fact, without networking grid computing would
not be possible. The recent growth in
communication capacity makes grid computing
practical, compared to the limited bandwidth
available when distributed computing was first
emerging.
 Transmission of content and job supervision within
the grid are important for sending jobs and the
required data to points within the grid (some jobs
require a large amount of data to be processed and
it may not always reside on the processor running
the job.
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3.  Computation The next most common resource on a
grid is obviously computing cycles provided by the
processors on the grid.
 The processors can vary in speed, architecture,
software platform, and storage apparatus.
 There are efforts underway to develop very high-
speed supercomputers. Whereas clustering is a
common approach at the TFLOPS speeds, grid
computing can also play a role in these initiatives by
refining architectures that link remote computers
into an assembly of loosely or tightly coupled
processors.
 At the business level, grid computing is expected by
the industry to be more practical than cluster-based
supercomputing.
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4.  Storage The next most common resource used in a grid is data
storage. In a grid environment, a file or data base can span several
physical storage devices and processors, bypassing size restrictions
often imposed by file systems that are preembedded with operating
systems. Storage capacity available to an application can be increased
by making use of the storage on multiple processors with a unifying
file system.
 Each processor on the grid usually provides some quantity of storage
for grid use. Storage can be “primary storage,” “secondary storage,”
or “tertiary storage.” Memory directly attached to a processor has fast
access capabilities but is volatile; this kind of memory is used to
cache data to serve as temporary storage for running applications.
 “Secondary storage” is generally implemented in hard disk drives,
such as with RAID (redundant array of inexpensive drives).
 “Tertiary storage” is generally implemented in near-real-time
accessible media such as tape or other permanent storage media.
Many grid systems use mountable networked file systems, such as
Network File System (NFS), Distributed File System (DFS), or General
Parallel File System (GPFS). Special grid database software can
“federate” a group of individual data bases and files to form a larger,
more inclusive data base.
A PHYSICAL VIEW
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5.  Scientific Instruments Grids, particularly an intergrid, can
provide shared access to expensive scientific equipment
or interconnect dispersed equipment into a larger overall
scientific tool. We will not discuss this issue further, since
our emphasis is on commercial applications.
 Software and Licenses Two issues are of interest to
organizations: application software and licensed
software. Regarding application software, the most basic
approach is to use the grid environment to allow the
application to run on an available processor on the grid
(rather than running locally.) Further along the transition
trajectory, one can modify the application to segment its
work in such a way that the separate parts can execute in
parallel on different grid processors. “scalability” is a
measure of how efficiently the multiple processors on a
grid are used. However, there may be limits to scalability.
A PHYSICAL VIEW
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