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sited at Leeds (Maxima and Snowdon) and one each at York (Pascali) and Sheffield
(Titania). The connecting middleware provides support for metering the usage
of the shared resources, for priority scheduling of jobs submitted to the Grid, for
monitoring if agreed deadlines for job completion are respected, and other func-
tionalities. Each participating university has allocated 25% of their node's compute
resource for White Rose Grid users. The remaining 75% share can be allocated as
required across the local academic groups and departments. Users across the three
universities are of two types: local users who have access only to the local facility
and White Rose Grid users who are allowed access to any node in the Grid. Another
example for a VO in a business environment is described in chapter 11 of this topic.
Moreover, chapter 12 presents a generic platform for hosting and establishment of
VOs.
A well-known example for a Community Grid is the already mentioned and
described SETI@HOME Grid.
3.5.2.5 Towards Open Global Grids
The different types of Grids described above also illustrate the evolution of Business
Grids (see fig. 3.6).
Fig. 3.6:
The Evolution of Business Grids (adapted from Weisbecker et al. 2008)
The existence of one type of Grid is the prerequisite for a subsequent type. For
example, Cluster Grids are usually components of an Enterprise Grid. A company
can extend its IT infrastructure and obtain additional resources either from a third
party (Utility Grid) or by participating and sharing resources in a VO. In general, the
evolution of Business Grids is characterized by increasing openness and increasing
scope of resource sharing across organizations. Requirements in terms of secu-
rity, privacy, reliability, scalability and flexibility become more important as the
openness of the Grid towards external resources increases. The evolutionary path
of Business Grids also shows that different degrees of maturity of the company
infrastructure and experiences are needed. Each higher level can only be achieved
