The Anatomy of the Grid 2
The real and specific problem that underlies the Grid concept is coordinated resource sharing
and problem solving in dynamic, multi-institutional virtual organizations. The sharing that we
are concerned with is not primarily file exchange but rather direct access to computers, software,
data, and other resources, as is required by a range of collaborative problem-solving and resource-
brokering strategies emerging in industry, science, and engineering. This sharing is, necessarily,
highly controlled, with resource providers and consumers defining clearly and carefully just what
is shared, who is allowed to share, and the conditions under which sharing occurs. A set of
individuals and/or institutions defined by such sharing rules form what we call a virtual
organization (VO).
The following are examples of VOs: the application service providers, storage service providers,
cycle providers, and consultants engaged by a car manufacturer to perform scenario evaluation
during planning for a new factory; members of an industrial consortium bidding on a new
aircraft; a crisis management team and the databases and simulation systems that they use to plan
a response to an emergency situation; and members of a large, international, multiyear high-
energy physics collaboration. Each of these examples represents an approach to computing and
problem solving based on collaboration in computation- and data-rich environments.
As these examples show, VOs vary tremendously in their purpose, scope, size, duration,
structure, community, and sociology. Nevertheless, careful study of underlying technology
requirements leads us to identify a broad set of common concerns and requirements. In
particular, we see a need for highly flexible sharing relationships, ranging from client-server to
peer-to-peer; for sophisticated and precise levels of control over how shared resources are used,
including fine-grained and multi-stakeholder access control, delegation, and application of local
and global policies; for sharing of varied resources, ranging from programs, files, and data to
computers, sensors, and networks; and for diverse usage modes, ranging from single user to
multi-user and from performance sensitive to cost-sensitive and hence embracing issues of quality
of service, scheduling, co-allocation, and accounting.
Current distributed computing technologies do not address the concerns and requirements just
listed. For example, current Internet technologies address communication and information
exchange among computers but do not provide integrated approaches to the coordinated use of
resources at multiple sites for computation. Business-to-business exchanges [57] focus on
information sharing (often via centralized servers). So do virtual enterprise technologies,
although here sharing may eventually extend to applications and physical devices (e.g., [8]).
Enterprise distributed computing technologies such as CORBA and Enterprise Java enable
resource sharing within a single organization. The Open Group’s Distributed Computing
Environment (DCE) supports secure resource sharing across sites, but most VOs would find it too
burdensome and inflexible. Storage service providers (SSPs) and application service providers
(ASPs) allow organizations to outsource storage and computing requirements to other parties, but
only in constrained ways: for example, SSP resources are typically linked to a customer via a
virtual private network (VPN). Emerging “Distributed computing” companies seek to harness
idle computers on an international scale [31] but, to date, support only highly centralized access
to those resources. In summary, current technology either does not accommodate the range of
resource types or does not provide the flexibility and control on sharing relationships needed to
establish VOs.
It is here that Grid technologies enter the picture. Over the past five years, research and
development efforts within the Grid community have produced protocols, services, and tools that
address precisely the challenges that arise when we seek to build scalable VOs. These
technologies include security solutions that support management of credentials and policies when
computations span multiple institutions; resource management protocols and services that support
secure remote access to computing and data resources and the co-allocation of multiple resources;
- 1
- 2
前往页