Grid Tools

Here you should find tools and usage examples for the basic grid operations.

All tests here were ran at lxplus5.cern.ch and environment from /cvmfs/cms.cern.ch/cmsset_defaults.sh AND /afs/cern.ch/cms/LCG/LCG-2/UI/cms_ui_env.sh

Before any interaction you need to create a proxy :

[lxplus429] /afs/cern.ch/user/s/samir/private/caltech/CMSSW_5_3_8/src > voms-proxy-init --voms=cms
Your identity: /DC=ch/DC=cern/OU=Organic Units/OU=Users/CN=samir/CN=695732/CN=Samir Cury Siqueira
Creating temporary proxy ..................... Done
Contacting  lcg-voms.cern.ch:15002 [/DC=ch/DC=cern/OU=computers/CN=lcg-voms.cern.ch] "cms" Done
Creating proxy ...................................... Done
Your proxy is valid until Wed Apr  2 07:48:53 2014

Remote storage access (single file)

Listing remote files

[lxplus429] /afs/cern.ch/user/s/samir/private/caltech/CMSSW_5_3_8/src > srmls -2 srm://cit-se.ultralight.org:8443/srm/v2/server?SFN=/mnt/hadoop/store/user/samir/
  /mnt/hadoop/store/user/samir//
      0 /mnt/hadoop/store/user/samir/1.root
      0 /mnt/hadoop/store/user/samir/a
      2684859832 /mnt/hadoop/store/user/samir/a.root
      17559490560 /mnt/hadoop/store/user/samir/access.log

Copying local file to remote Storage Element

(Samir) : My Grid certificate has some problems with a recent migration (SHA2/VOMS), so I couldn't paste here the output, only the command that is supposed to work. If anyone manages t o do it successfully please edit the twiki and add the output to the example below :

[lxplus429] /afs/cern.ch/user/s/samir/private/caltech/CMSSW_5_3_8/src > srmcp -debug -2 file:////$PWD/a.root  srm://cit-se.ultralight.org:8443/srm/v2/server?SFN=/mnt/hadoop/user/samir/cerntest256.root

To copy the file in the other sense (remote SE) to local, you just need to invert the order in the same command above. The -debug flag is optional but gives a lot of insight of what is happening.

Xrootd access via ROOT

Some users claim that when using CMSSW, Xrootd performance is good, but when using pure ROOT it is poor, here are some notes about the needed tuning, from Emanuele, currently untested :

Suggestion from the IT on how to speed up the ROOT access
in the same way it is done for the CMSSW jobs.

Basically we have to tune this:

http://root.cern.ch/root/html/TTreeCache.html

and mainly:

T->SetCacheSize(cachesize); // use cachesize=10000000 (~10MB)  up to 30 MB

and

T->SetCacheLearnEntries(5); // let root discover which branches you use or else look at other examples to configure the used branches

-- Main.samir - 2014-04-01