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Proposal for the LHCb Italian Tier-2

This proposal outlines the construction of a Tier-2 host in Bologna for LHCb analysis, optimizing resource sharing between Tier-1 and Tier-2 facilities.

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Proposal for the LHCb Italian Tier-2

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  1. Proposal for the LHCbItalian Tier-2 Domenico Galli, Bologna INFN CSN1 Roma, 17.5.2005

  2. Aim of LHCb Tier-2s • In the LHCb Computing Model Tier-2s are used for Monte Carlo production. • 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. • In previous presentations these Tier-2 resources were kept together with Tier-1 resources; now, following referees’ suggestion, they have been kept apart since they have to be approved by CSN1. Proposal for 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 Proposal for 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 Proposal for the LHCb Italian Tier-2. 4 Domenico Galli

  5. Why LHCb Analysis at Tier-1? (III) • This model would allow maximum flexibility in moving resources back/forth between Tier-2 and Tier-1 to optimize resource exploitation. • E.g.: resources can be moved from Tier-2 to Tier-1 to satisfy peak analysis request, or vice versa in case on peak Monte Carlo request. • In this sense the distinction between Tier-1 and Tier-2 LHCb resources evaporates… Proposal for the LHCb Italian Tier-2. 5 Domenico Galli

  6. CNAF Tier-1 (reconstruction, stripping, analysis) LHCb Tier-2 (Monte Carlo) LAN Gateway WAN LHCbTier-3 LHCbTier-3 LHCbTier-3 LHCbTier-3 LHCbTier-3 LHCbTier-3 LHCbTier-3 LHCbTier-3 Overview of Italian LHCb Computing Resources Proposal for the LHCb Italian Tier-2. 6 Domenico Galli

  7. 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. Proposal for the LHCb Italian Tier-2. 7 Domenico Galli

  8. LHCb Tier-2 Size and Cost (II) Proposal for the LHCb Italian Tier-2. 8 Domenico Galli

  9. LHCb Tier-2 Size and Cost (III) • However the Computing Model is not Bible! • It is only a raw estimate of the needs, based on today knowledge and understanding. • If additional resources will be available in the forecoming years for the LHCb Tier-2, these could result precious. • Furthermore these resources could be moved back and forth to/from Tier-1 on need, to allow most optimized usage. Proposal for the LHCb Italian Tier-2. 9 Domenico Galli

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