DCache

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This article is outdated. The recommended way of accessing files on LOCALGROUPDISK is now (2016) the ROOT protocol

Using dCache @ LRZ

LRZ dCache is standard repository for AOD and DESD input data but also for user-job output data being copied via DQ2 to LRZ-LMU_LOCALGROUPDISK or LRZ-LMU_SCRATCHDISK space-tokens.

There are several options how to get or access a file in LRZ dCache:

  • first one has to get a list of files from DQ2 (DQ2 setup):
# get datasets
dq2-list-dataset-site -n 'data10*NTUP_MINBIAS.*'  LRZ-LMU_LOCALGROUPDISK
# list files in dataset
dq2-ls -f -p -L LRZ-LMU_LOCALGROUPDISK \
 data10_7TeV.00152273.physics_MinBias.merge.NTUP_MINBIAS.f239_p127_tid125130_00
# output are so-called SRM names
# convert into dcache local file access names:
dq2-ls -f -p -L LRZ-LMU_LOCALGROUPDISK \
 data10_7TeV.00152273.physics_MinBias.merge.NTUP_MINBIAS.f239_p127_tid125130_00 
 | sed 's%srm://lcg-lrz-srm.grid.lrz.de%dcap://lcg-lrz-dcap.grid.lrz.de%'

The resulting files can either be

  • opened and processed directly in Root :
    TFile * f = TFile::Open("dcap://lcg-lrz-dcap.grid.lrz.de/pnfs/lrz-muenchen.de/data/atlas/dq2/atlaslocalgroupdisk/data10_7TeV/NTUP_EGAM/f247_p129/
    data10_7TeV.00153030.physics_MinBias.merge.NTUP_EGAM.f247_p129_tid126434_00/NTUP_EGAM.126434._000004.root.1")
    

    (Some Root versions have problems accessing files in dCache, use the standard Root setup)

  • or you download/copy it to scratch first:
    dccp -A dcap://lcg-lrz-dcap.grid.lrz.de/pnfs/lrz-muenchen.de/data/atlas/dq2/atlaslocalgroupdisk/data10_7TeV/NTUP_EGAM/f247_p129/
    data10_7TeV.00153030.physics_MinBias.merge.NTUP_EGAM.f247_p129_tid126434_00/NTUP_EGAM.126434._000004.root.1 \
    $PTMP