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The LHCb Italian Tier-2

The LHCb Italian Tier-2. Domenico Galli, Bologna. INFN CSN1 Roma, 10.10.2005. Aim of LHCb Tier-2s. In the LHCb Computing Model Tier-2s are used (at least in countries also provided with a Tier-1) as a pure centrally scheduled Monte Carlo simulation facility .

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The LHCb Italian Tier-2

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  1. The LHCb Italian Tier-2 Domenico Galli, Bologna INFN CSN1 Roma, 10.10.2005

  2. Aim of LHCb Tier-2s • In the LHCb Computing Model Tier-2s are used (at least in countries also provided with a Tier-1) as a purecentrally scheduled Monte Carlo simulation facility. • In the LHCb Computing Model Analysis is not performed on Tier-2s. • A LHCb Tier-2 consists in a PC-farm with a small disk buffer (3 TB in steady state) used as a temporary cache until data transfer to Tier-1. • LHCb-Italy proposes to build 1 Tier-2 hosted at Bologna-CNAF, together with Italian Tier­1. The LHCb Italian Tier-2. 2 Domenico Galli

  3. Why LHCb Analysis at Tier-1? • LHCb analysis jobs consist in selecting the events (stripped DST) stored at Tier-1 to focus on one particular analysis channel: • Typical analysis jobs run on a~106 event sample. • Some analysis jobs will run ona larger ~107 event sample. • Average event reduction of a factor of 5. • Analysis input is completely stored at each Tier-1. • Analysis output (20-200 GB) can be processed by a small Tier-3 facility. Available at each Tier-1 Available at each Tier-1 SelectedDST+RAW119 TB Event TagCollection20 TB Physics Analysis n-tuple / User DST + User TAGTypical: 20 GB Large: 200 GB Local Analysis The LHCb Italian Tier-2. 3 Domenico Galli Paper

  4. Tier-1 Tier-2 139 TB Output 20-200 GB DST+RAW+TAG139 TB 139 TB Buffer LAN WAN Tier-1 Output 20-200 GB DST+RAW+TAG139 TB 139 TB Why LHCb Analysis at Tier-1? (II) • Comparison between 2 models: • Analysis job at Tier-2: • Analysis job at Tier-1: • Data accessed at Tier-1 per analysis job are the same. • But the second is faster and less expensive in terms of hardware, infrastructure, staff resources and WAN load. LAN The LHCb Italian Tier-2. 4 Domenico Galli

  5. Why Tier-2 at CNAF? • This model would allow maximum flexibility in moving resources back/forth between Tier-2 and Tier-1 to optimize resource exploitation. (to satisfy peak MC/analysis request). • Simply by means of a software operation. • No competition among Italian sites on Tier-2 resources, since MC production is centrally scheduled. • Italian LHCb people involved in computing are mainly located in Bologna. The LHCb Italian Tier-2. 5 Domenico Galli

  6. Tier-2 at CNAF • Given the growing profile, LHCb Tier-2 is at maximum a +10% perturbation of CNAF Tier-1 resources. • Same building. • Same cooling system. • Same fire alarm and surveillance. • Same network. • Same electric power and UPS. • Etc. • Same trained and skilled management and technical staff. • LHCb experiment staff from Bologna • Already heavily involved in LHCb computing; • Established strict collaboration with the CNAF staff. The LHCb Italian Tier-2. 6 Domenico Galli

  7. LHCb Tier-2 Exploitation in the Next Years • From now on, practically speaking, an almost continuous MC production is foreseen for LHCb. Mainly for: • Physics studies; • HLT studies. • Order of 100's Mevents/year. The LHCb Italian Tier-2. 7 Domenico Galli

  8. LHCb Tier-2 Size and Cost • We are sizing the Italian Tier-2 to be 15% of the total Tier-2 resources of the whole LHCb collaboration. • 15% = Italian fraction of CORE funds; • 15% = fraction of Italian physicists with respect of the total involved in the LHCb experiment. The LHCb Italian Tier-2. 8 Domenico Galli

  9. LHCb Tier-2 (@CNAF): Additional Size and Cost (according to LHCb Computing Model) The LHCb Italian Tier-2. 9 Domenico Galli

  10. LHCb Tier-2 (@CNAF): Additional Infrastructures 1 kSi2k → 110 W 1 TiB → 70 W The LHCb Italian Tier-2. 10 Domenico Galli

  11. LHCb Requests for 2006 • 190 k€: Tier-2 resources (95 dual-processor box + 1 TiB Disk). • Since resources are allocated at CNAF, resource management could be flexible: • CPUs can be moved from Tier-1 queues to Tier-2 queues and back with software operations. • But Tier-2 have to be logically separated by Tier-1 (e.g.: different batch queues). The LHCb Italian Tier-2. 11 Domenico Galli

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