ALICE Physics Data Challenge’04

1. P.Hristov March 19, 2004 CERN ALICE Physics Data Challenge’04

2. Goals(http://cern.ch/fca/ALICE-DCs.doc) • Determine readiness of the off-line framework for data processing • Validate the distributed computing model • PDC’2004:10% test of the final capacity • Complete chain used for trigger studies • Prototype of the analysis tools • Comparison with parameterized MC • Simulated RAW data • PDC’04 physics: hard probes (jets, heavy flavours) & pp physics

3. Physics Data Challenge'2004 • Simulation: 10^5 Pb-Pb + 10^7 p-p 102 TB • 450 KSI2K (~ tier-1 capacity) x 3 months • Distributed production, then data are shipped to CERN • Reconstruction: 5x10^6 Pb-Pb+10^7 p-p 187 TB • Reconstruction is shared between CERN & outside centres according to available resources • Data originate from CERN • Analysis: 5x10^6 Pb-Pb+10^7 p-p 13 TB • See http://aliweb.cern.ch/people/phristov/PDC04.html

4. PDC’04 Strategy • Part 1: underlying events • Distributed simulation, production of summable digits, digitization, clusterization, reconstruction, PID, and generation of ESD • Data transfer to CERN: kinematics, track references, summable digits (hits for some detectors) • Part 2: signal events & test of CERN as data source • Distributed simulation, production of summable digits, merging, digitization, clusterization, reconstruction, PID, generation of ESD • Part 3: distributed analysis

5. AliReconstruction AliSimulation ESD AliAnalysis AliRoot Layout G4 G3 FLUKA AliEn ISAJET AliRoot Virtual MC HIJING EVGEN MEVSIM HBTAN STEER PYTHIA6 PDF PMD EMCAL TRD ITS PHOS TOF ZDC RICH HBTP STRUCT CRT START FMD MUON TPC RALICE NEW ROOT

6. Current Status • Major changes in the last year • New multi-file I/O finally in full production • New coordinate system • New reconstruction and simulations classes • First attempt at the ESD and analysis framework • Improvements in reconstruction and simulation • Clearly the system works well, however a lot of changes to come • ESD: the philosophy is still evolving • Introduction of FLUKA and new geometrical modeller • Development of the analysis framework • Raw data for all the detectors -- we need them for the data challenge • Introduction of the condition database infrastructure

7. PDC’04 Schema AliEn job control Data transfer Production of RAW Shipment of RAW to CERN Reconstruction of RAW in all T1’s CERN Analysis Tier2 Tier1 Tier1 Tier2

8. Signal-free event Merging Merged signal

9. Server LCG PFN Catalog Catalog LCG LFN LCG LFN = AliEn PFN AliEn, Genius & EDG/LCG User submits jobs Alien CE LCG UI Alien CEs/SEs LCG RB LCG CEs/SEs

10. ALICE PDC04 & LCG • All the production is started via AliEn, the analysis will be done via Root/Proof/AliEn • LCG-2 is one CE element of AliEn, which integrates seamlessly LCG and non LCG resources • If LCG-2 works well, it gets a large amount of jobs, and it is used heavily • If LCG-2 does not work well, AliEn will privilege other resources, and it will be less used • In all cases we will use LCG-2 as much as possible • We will not need to take any decision: the performance of the system will decide for us

11. Short History • Jan 03: Requirements for ALICE PDC04 presented to PEB • End Dec 03: Announcement of LCG-2 by mid February 2004 • Beg Jan 04: Decision to delay PDC04 by one month waiting for LCG-2 • Beg Jan 04: LCG announces that there will be no SE in LCG-2 • Beg Feb 04: The WAN resources allocated by LCG for data storage are insufficient/inadequate • Mid Feb 04: Development of an ALICE solution, developed in haste and working against all odds! • End Feb 04: IT has also come up with a solution responding to a CMS requirement • End Feb 04: Production started, new sites being added • End Feb 04: Tape vault flooded -- our tapes have been spared • Beg Mar 04: castor nameserver has to be reinstalled (running on Linux 6.2) • Beg Mar 04: castor servers have to be reinstalled for security • Beg Mar 04: LCG RB works differently on the different centres. • e.g. CNAF has to be switched on and off by hand, otherwise it “swallows” all the jobs! • Beg Mar 04: we are obtaining now close to 10 TB • Mid Mar 04: Files on the IT-provided pool are erased before being copied on tape

12. Data Challenge Statistics Picture from yesterday, 18/03/2004

13. Data Challenge Statistics

14. Data Challenge Statistics

15. Considerations • LCG is providing a lot of cycles • ALICE is the first to use the system for production • This required continuous efforts and interventions (ALICE and LCG), particularly due to lousy workload scheduling and lack of stability • The lack of an SE will make reconstruction and analysis possible only under AliEn • Relations with LCG are in general good • They are sincerely willing to help • But the system was not fully prepared for our PDC’04 • LCG PR / planning can be improved!

16. Considerations (cont) • Next time we will start six months before! • LCG needs to be “prompted” for resources and support • Some ALICE people did not get well the philosophy of a DC • The period Jan-Feb was well spent • Changes in AliRoot improved performance and results • AliEn now has a more advanced SE solution • The Offline members reacted extremely well to pressure and the exercise is definitely very useful • We will reach the objectives!

17. ALICE Physics Data Challenges NEW NEW