Utilisation d’Xrootd dans
ATLAS
LCG-France 7-juillet-2008
07-July-2008
Eric Lançon
1
Xrootd : why?

LHC data volume : I/O problem…
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
See J.P. Meyer last meeting :
http://indico.in2p3.fr/conferenceDisplay.py?confId=543
Current ATLAS batch analysis:
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Inputs copied to /tmp of WN
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Some conditions data read-in at beginning of job through
dcap…
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Cannot scale with data volume or too high segmentation of
inputs
Kill dCache pools…
dCache cannot sustain high load of analysis jobs and
certainly not interactive analysis
Xrootd under tests for batch analysis at Lyon

Inputs not copied to WN, direct reading of Xrootd files
07-July-2008
Eric Lançon
2
Xrootd in ATLAS

SLAC :

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data storage,
SRM interfaced
BNL :

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data storage, No SRM interface
PROOF

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Wisconsin :

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http://www.usatlas.bnl.gov/twiki/bin/view/AtlasSoftw
are/ProofTestBed.html
PROOF + Condor
CC-Lyon :

data storage, No SRM interface
07-July-2008
Eric Lançon
3
SRM & Xrootd

BeStMan-xrootd is a generic SRM v2.2 load
balancing frontend for GridFTP servers.




http://wt2.slac.stanford.edu/xrootdfs/bestmanxrootd.html
Developed by LBL
Used for SLAC T2 to get ATLAS data from
distribution system (DDM)
The only ATLAS full Xrootd site
07-July-2008
Eric Lançon
4
Xrootd at BNL

Xrootd disk pool for



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Batch analysis
PROOF
No SRM interface
Data sets


stored on Xrootd pool ‘on demand’
known by ATLAS DDM system
07-July-2008
Eric Lançon
5
07-July-2008
Eric Lançon
6
Xrootd at Lyon

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Prototype…
Xrootd disk pool for

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
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No SRM interface
Data sets

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

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Batch analysis
Interactive analysis but not //-analysis (PROOF)
stored on Xrootd pool via tool developed by J.Y. Nief
(/pnfs mounted on ccsrb15)
Xrootd pool as a stagein area, dCache as repository
Not known to ATLAS DDM system
Outputs to dCache
Dedicated pAthena queue working
07-July-2008
Eric Lançon
7
Xrootd at Lyon : outlook

Do not wait for users to come and use resources

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When they will come (soon?) they will ask for usable,
stable and efficient resources
If not they will complain and go somewhere else(?)
Xrootd analysis queue will be set as default for ATLAS
at Lyon
Dedicated WN pool (BQS queue) to tune I/O
performances
HPSS as backend
Interactive // analysis (PROOF) ?
07-July-2008
Eric Lançon
8
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Eric Lançon
9
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Eric Lançon
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Eric Lançon
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Eric Lançon
12
PROOF-Condor

http://www.cs.wisc.edu/condor/CondorWeek2
008/condor_presentations/ganis_proof.pdf
07-July-2008
Eric Lançon
13
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Eric Lançon
14
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Eric Lançon
15
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Eric Lançon
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Eric Lançon
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Eric Lançon
18
Federate PROOF cluster

A cluster which results from grouping
together machines which may reside on
different geographical domains.

http://root.cern.ch/twiki/bin/view/ROOT/XpdMultiM
aster
07-July-2008
Eric Lançon
19
Useful for distributed T2/3 ?
07-July-2008
Eric Lançon
20
07-July-2008
Eric Lançon
21
gLitePROOF

See ATLAS talk at T2-T3 meeting
20 March 2008


http://indico.in2p3.fr/conferenceOtherViews.py?vie
w=standard&confId=619
See Karim Bernardet talk at ATLAS Analysis
meeting 27 May 2008

http://indico.cern.ch/conferenceOtherViews.py?vie
w=standard&confId=33416
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Eric Lançon
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