dCache is a disk-based distributed storage system with a unique tree structure. At CC-IN2P3, the dCache provides local data access through an XRootD door and a standard remote access protocol (SRM, “Storage Resource Manager”).
This service is interfaced with the HPSS service, so it can be used as a disk cache in front of a tape-based backend. But it can also be used as a pure disk storage service.
Today dCache hosts data from Virtual Organizations (VO) belonging to the LHC and EGI collaborations.
Three XRootD-protocol endpoints are available on dCache for LHC experiments: - ccxrootdatlas.in2p3.fr (ATLAS) - ccxrootdcms.in2p3.fr (CMS) - ccxrootdlhcb (LHCb)
Example of a file copy using the XRootD protocol:
% xrdcp root://ccxrootdatlas.in2p3.fr:1094//pnfs/in2p3.fr/data/atlas/atlasdatadisk/rucio/mc15_14TeV/0f/20/AOD.10073441._001377.pool.root.1 /scratch/testxrd
SRM (gridftp) protocol¶
The gridftp protocol is based on grid certificate authentication and needs a proper grid proxy file. It permits file transfers from and to dCache.
Example of a command to transfer a local file to dCache:
% gfal-copy file:///scratch/myfile srm://ccsrm.in2p3.fr:8443/pnfs/in2p3.fr/data/dteam/myfile
Example of a command to transfer a dCache file locally:
% gfal-copy srm://ccsrm.in2p3.fr:8443/pnfs/in2p3.fr/data/dteam/monfichier file:///scratch/monfichier