Proposal for the LHCb Italian Tier-2 Domenico Galli, Bologna INFN CSN1 Roma, 17.5.2005
Proposal for the LHCb Italian Tier-2. 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
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 on a 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 Selected DST+RAW 119 TB Event Tag Collection 20 TB Physics Analysis n-tuple / User DST + User TAG Typical: 20 GB Large: 200 GB Local Analysis Proposal for the LHCb Italian Tier-2. 3 Domenico Galli Paper
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. Tier-1 Tier-2 DST+RAW+TAG 139 TB Buffer Output 20-200 GB 139 TB WAN LAN Tier-1 DST+RAW+TAG 139 TB Output 20-200 GB 139 TB LAN Proposal for the LHCb Italian Tier-2. 4 Domenico Galli
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
Overview of Italian LHCb Computing Resources CNAF LAN LHCb Tier-3 WAN Tier-1 (reconstruction, stripping, analysis) LHCb Tier-2 (Monte Carlo) Gateway Proposal for the LHCb Italian Tier-2. 6 Domenico Galli
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
LHCb Tier-2 Size and Cost (II) Strictly according to current LHCb Computing Model 2006 2007 2008 2009 2010 total CPU [€/Si2k] 0.58 0.38 0.25 0.17 0.12 Disk [€/GB] 2.25 1.40 0.88 0.55 0.34 CPU running [MSi2k] 0.69 1.15 Disk running [TB] 1 2 3 CPU replacement [MSi2k] 0.35 Disk replacement [TB] CPU to be acquired [MSi2k] 0.46 Disk to be acquired [TB] CPU cost [k€] 196.5 132.4 117.1 56.1 43.3 545.5 Disk cost [k€] 2.2 1.4 0.9 0.5 0.3 5.4 Total cost [k€] 198.7 133.8 118.0 56.7 43.7 550.9 Proposal for the LHCb Italian Tier-2. 8 Domenico Galli
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