Bridge over muddled waters of Grid storage
Mon 17 Dec 2007
Two islands of Grid storage technology have now been joined, with a successful demonstration bridging the key technologies of the Storage Resource Broker (SRB) and Storage Resource Manager (SRM). The demonstration was run at Supercomputing 2007 in Reno, Nevada, on behalf of a GridPP-led team from Rutherford Appleton Laboratory.
SRM and SRB are both ways of accessing the storage available on a Grid - either tape, disks or arrays of disks. Usually, storage elements running SRB can't be seen by a Grid running SRM, and vice versa. Most Grids run one or the other technology, but if different Grids are to interoperate the two standards will need to work together.
Jens Jensen of RAL, who led the team building the demonstration, says, "SRM and SRB are traditionally the two separate 'storage islands' in Grids, each providing interoperability within its own island, but not between the islands. We used the GridFTP protocol and advanced data management tools from the EGEE project to transfer data between SRM and SRBs, and bridge these islands."
The team built on a GridFTP server developed for SRB, managing to make an SRB look like a `Classic Storage Element'. This let the gLite tools transfer files between SRMs and SRBs. More details about the demonstration can be found on the GridPP Wiki at http://www.gridpp.ac.uk/wiki/SRM_SRB_interoperability
One of Jens's activities is working on interoperability between the UK's two main science Grids: GridPP, the particle physics Grid, which runs various implementations of SRM, and the National Grid Service, which mainly runs SRB. This work also opens up opportunities for other Grids to share data - for example between Worldwide LHC Computing Grid and the US TeraGrid.
Erwin Laure is the technical director of the EGEE project, and he also coordinates the Grid Interoperability Now activities in the Open Grid Forum. He says, "Interoperation of different Grid infrastructures is a necessity for many applications, and the OGF GIN community aims at pragmatic solutions achieving interoperation. The interoperation between the two most commonly deployed data solutions, SRM and SRB, achieved by Jens's GridPP/STFC team is a great step forward towards achieving this goal."
Alex Sim of Lawrence Berkeley National Laboratory in the US demonstrated the data transfer for the UK team at Supercomputing. He explains, "The Supercomputing 2007 demo showed interoperability of 11 different SRM implementations around the world based on the same specification, including data transfers between an SRB at Rutherford Appleton Laboratory and BeStMan SRM at Lawrence Berkeley National Laboratory. This caused great interest among delegates, and it is of interest for scientists - especially in the Worldwide LHC Computing Grid Project, as they can now access data directly in SRB."
Jens is particularly enthusiastic about how well the current work fits the GIN group, "The important aspect of this work is that it builds on existing tools and requires no development effort. It really is Grid Interoperability Now!"
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