Information Technology Reference
In-Depth Information
job management provides mechanisms to query
the status of the job as well as perform opera-
tions such as canceling the job. The application
may need to utilize these capabilities to provide
feedback to the user or to clean up or free up
resources when required. For instance, if one job
within an application fails, other jobs that may be
dependent on it may need to be cancelled before
needlessly consuming resources that could be
used by other jobs.
registers its local information with the GIIS, which
can optionally also register with another GIIS, and
so on. MDS clients can query the resource infor-
mation directly from GRIS (for local resources)
and/or a GIIS (for grid-wide resources).
It is important to fully understand the require-
ments for a specific job so that the MDS query can
be correctly formatted to return resources that are
appropriate. The user has to ensure that the proper
information is in MDS. There is a large amount
of data about the resources within the Grid that is
available by default within the MDS. However,
if the application requires special resources or
information that is not there by default, the user
may need to write her own information providers
and add the appropriate fields to the schema. This
may allow the application or broker to query for the
existence of the particular resource/requirement.
Applications and Resource
Information Services
An important part of the process of grid-enabling
an application is to identify the appropriate (if not
optimal) resources needed to run the application,
i.e. to submit the respective job to. The service
which maintains and provides the knowledge
about the Grid resources is the Grid Information
Service (GIS), also known as the Monitoring and
Discovery Service (e.g. MDS in Globus (Jacob,
2003). MDS provides access to static and dynamic
information of resources. Basically, it contains the
following components:
Applications and Data Management
Data management is concerned with collectively
maximizing the use of the limited storage space,
networking bandwidth, and computing resources.
Within the application, data requirements have
been built in which determine, how data will
be move around the infrastructure or otherwise
accessed in a secure and efficient manner. Stan-
dardizing on a set of Grid protocols will allow
to communicate between any data source that is
available within the software design. Especially
data intensive applications often have a federated
database to create a virtual data store or other
options including Storage Area Networks, net-
work file systems, and dedicated storage serv-
ers. Middleware like the Globus Toolkit provide
GridFTP and Global Access to Secondary Storage
data transfer utilities in the Grid environment.
The GridFTP facility (extending the FTP File
Transfer Protocol) provides secure and reliable
data transfer between Grid hosts.
Developers and users face a few important data
management issues that need to be considered in
application design and implementation. For large
•
Grid Resource Information Service
(GRIS), the repository of local resource
information derived from information
providers.
•
Grid Index Information Service (GIIS),
the repository that contains indexes of re-
source information registered by the GRIS
and other GIISs.
•
Information providers, translate the prop-
erties and status of local resources to the
format defined in the schema and configu-
ration files.
•
MDS client which initially performs a
search for information about resources in
the Grid environment.
Resource information is obtained by the infor-
mation provider and it is passed to GRIS. GRIS
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