Database Reference
In-Depth Information
Tape1Disk1
Tape1Disk0. On some systems this can be implemented as a
metadata operation only, while other systems may require more opera-
tions to guarantee such a transition.
Tape1Disk0
Tape1Disk1. This transition is implemented with some re-
strictions: The request will complete successfully but the files will re-
main on tape. The files will be actually recalled from tape to disk only
after an explicit request is executed. This is done in order to avoid un-
necessarily scheduling of a big set of files for staging and therefore to
smooth operations, in particular for those MSSs that do not have a
scheduler.
Tape0Disk1
Tape1DiskN. Such transitions are not supported at the start
of LHC (if ever). For physics validation operations, since the amount
of data to transfer to tape after the validation is not big (only 1%-
2% of total data), a change from Tape0Disk1 to Tape1DiskN can be
approximated by copying the files to another part of the name space,
specifying Tape1DiskN as the new storage class, and then removing the
original entries.
3.4.4.5
The Grid Storage Systems Deployment Working Group
In January 2007 the Grid Storage Systems Deployment (GSSD) working
group 10 , 27 - 29 was established with the following main goals:
Testing of SRM v2.2 implementations for compliance and interoperability.
Establishing a migration plan from SRM v1.1 to SRM v2.2 so that the experi-
ments can access the same data through the two protocols transparently.
Coordinating with sites, experiments, and developers the deployment of
the various SRM v2.2 implementations and the corresponding storage
classes.
Coordinating the definition and deployment of an information schema for the
storage element to allow for the relevant aspects of SRM v2.2 services
to be discoverable through the WLCG information system.
Coordinating the provision of the necessary information by the stor-
age providers in order to monitor the status and usage of storage
resources.
It took until the autumn of 2007 for CERN and the Tier-1 sites to start
putting SRM v2.2 services into the WLCG production infrastructure, with
known deficiencies to be corrected in later versions. Further improvements
were implemented after significant operational experience had been gained
during a final set of large-scale tests, the Common Computing Readiness Chal-
lenge, which took place in February and May 2008. The work of the GSSD
has carried on throughout 2008 and into 2009.
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