Database Reference
In-Depth Information
It might imply running variations of the program several times on the same
set of data. Once the process is finished, the result is stored on tape.
The implicit storage, data, and transfer requirements are as follows:
Data needs to be accessible from the storage system, that is, MSSs and disk
systems. The corresponding data servers need to provide the required
performance.
Data transfer tools need to be in place that have access to the source storage
system and can transfer data to another storage system at a different
site/tier. Since the physics activities and therefore also the data transfers
are scheduled, the latter can be optimized: Bandwidth can be “reserved”
by
prioritizing
the requests of a particular physics group and reducing
the ones of other physics groups or individual users.
Once data has arrived at the site, computing and storage
resources
must be
dynamically or statically
reserved
for a particular user group.
It should be possible to express
ownership of resources
and specify
autho-
rization patterns
.
In order to ensure resource sharing,
quotas
should essentially be enforced in
a transparent way so that several groups within the experiment or even
multiple experiments can concurrently use the resources at a site.
Resource usage and
status
should be
monitored
and published so that busy
resources are not selected for further computing and/or storage tasks.
If the needed data is on tape, it must first be transferred to disk for online
access. Therefore, transparent staging tools must be available.
Specific
file access protocols
need to be supported by the storage facility, so
that applications limited to using only those protocols can be executed.
Once data is analyzed, the relevant output can be saved on tape if deemed
important. Therefore, tools to archive the results on tape and register
them on the grid are necessary.
Physicists should be provided with the necessary tools to
manage space
,
for instance in case the storage system does not remove unneeded files
automatically.
Grid operators and/or site administrators that take care of the execution
and monitoring of data transfers as well as the allocation of CPU power to
the physics group can further support and optimize the actual execution of
this use case scenario.
3.4.3.3
Calibration Study
During the run of the LHC, particles pass through detectors that have to be
aligned and calibrated in order to allow for correct physics analysis. A physics
group might work on the calibration study and detect problems with the cali-
bration and alignment parameters. In such a case, some of the reconstruction
