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INFN Computing for LHCb

INFN Computing for LHCb. Domenico Galli, Umberto Marconi, and Vincenzo Vagnoni. Genève , February 15, 2001. Changes in INFN Computing Plans. Before December 2000: Plans for the Tier-1 were different for the 4 LHC experiments.

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INFN Computing for LHCb

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  1. INFN Computing for LHCb Domenico Galli, Umberto Marconi, andVincenzo Vagnoni Genève, February 15, 2001

  2. Changes in INFN Computing Plans • Before December 2000: • Plans for the Tier-1 were different for the 4 LHC experiments. • ALICE, ATLAS and CMS planned for a Tier-1 “distributed” among 2 or 3 sites. • After December 2000: • INFN plans to build a Regional Computing Centre (RCC), located at CNAF (Bologna) in the first instance, which: • acts as a unique “concentrated” Tier-1 for all the 4 LHC experiments, • acts as Tier-A for BaBar, • Supplies enough computing power and off-line storage for VIRGO. INFN Computing for LHCb Domenico Galli, Umberto Marconi and Vincenzo Vagnoni

  3. INFN computing projects for LHC • Short term project: INFN-Grid. • Started (and funded) on January 1, 2001. Term: 3 years. • Funds: 1.5 M€ (2001) + 4 M€ (2002) + 4 M€ (2003). • Aim: • developing Grid software in collaboration with DATAGRID; • developing Grid test-bed; • funding hardware and consumables needed in Tier-n prototypes testing. • Long term project: INFN-RCC. • Will start before April 2001. • Funds: about 22 M€ available soon. • Aim: • Supply the computing resources for VIRGO and the Tier-A computing centre for BaBar; • Build the final Italian Tier-1 Regional Centre for LHC (30% in 2005, 60% in 2006, 100% in 2007). INFN Computing for LHCb Domenico Galli, Umberto Marconi and Vincenzo Vagnoni

  4. Short Term: LHCb Funded Investments in 2001 INFN Computing for LHCb Domenico Galli, Umberto Marconi and Vincenzo Vagnoni

  5. Short Term: LHCb Further Investments in 2001 • Availability of more funds, later in 2001, is conditional to: • The production of a believable computing model for 2001 (given the present WAN bandwidth). • The evidence of a high load of the installed CPUs. • The use of produced MC by Italian institutes for their own analyses. INFN Computing for LHCb Domenico Galli, Umberto Marconi and Vincenzo Vagnoni

  6. 2001 Farm for LHCb-Italy • LHCb-Italy plans to build a diskless (and swapless) farm with a concentrated file server (NAS). • Cheaper in hardware: both initial purchase and subsequent maintenance; • Cheaper in software support; • More robust for demanding computing environments: no moving parts in the PC; • Swapping and paging are not needed in job processing nodes: • because their memory consumption is predictable; • it is absolutely not convenient that they have any memory swapped. • A disadvantage can be the network load during simultaneous booting. But it can be completely overcome by using MTFTP (multicast TFTP). INFN Computing for LHCb Domenico Galli, Umberto Marconi and Vincenzo Vagnoni

  7. 2001 Farm for LHCb-Italy (II) INFN Computing for LHCb Domenico Galli, Umberto Marconi and Vincenzo Vagnoni

  8. 2001 Components (Motherboards, Racks, NAS, Switches) INFN Computing for LHCb Domenico Galli, Umberto Marconi and Vincenzo Vagnoni

  9. Preliminary Farm Tests • NFS operation  • NFS is needed to collect MC output on RAID disk arrays (instead of spread them among hundreds of non-redundant local disks). • MC output rate is low (a few kB/s) compared with NFS performances (~ 7-10 MB/s on Fast Ethernet). • Swap-less operation  • Memory demand by job execution nodes is stable. • Swap area is useless on job execution nodes (but is required on login nodes). • Monte Carlo performances do not depend on the presence of a swap area. • NFS functionalities  • Kernel version 2.2.18 or higher required on clients, in order to allow broken setuid on NFS root. INFN Computing for LHCb Domenico Galli, Umberto Marconi and Vincenzo Vagnoni

  10. Preliminary Farm Tests (II) • RAM errors  • It seems that after the Taiwan earthquake in 1999, the quality of memories in the market has dropped significantly. • Memtest86 program can detect cross-talk errors in RAM modules without ECC control; • Badram kernel module can fix them (marking bad memory locations as “permanently used”). • Switching nodes on and off from remote. • Wake-on-LAN (from Intel Wired-for-Management) allows to switch on computer from remote, but does not allow to switch them off.  • Wake-on-LAN not useful to reboot a hung-up node.  • A different solution must be found (e.g. remote power switch control, products by BayTech, Western Telematic, National Instrument). INFN Computing for LHCb Domenico Galli, Umberto Marconi and Vincenzo Vagnoni

  11. Preliminary Farm Tests (III) • Network boot  • Takes a few seconds more than a boot on local HD. • Required BOOT-PROMon Network Interface Card. • PXE(Preboot Execution Environment from Intel Wired-for-Management specifications) compliance is not mandatory, but strongly preferred. • PXE allows a multiple boot-server configuration, to provide load balancing and redundancy in a large installation. • MTFTP (Multicast Trivial File Transfer Protocol) is not an IETF standard. PXE defines a proprietary implementation with wide spread usage. 4 phases: listen a matching MTFTP session already in progress; open a new MTFTP session; receive MTFTP data with acknowledgement; close a MTFTP session. • Intel-Red Hat Linux implementation of PXE 2.1 exists and works. We tested it with 3Com EtherLink 3C905C-TX-M NIC. Linux implementation of PXE 32/64 almost ready. INFN Computing for LHCb Domenico Galli, Umberto Marconi and Vincenzo Vagnoni

  12. PXE Boot Sequence INFN Computing for LHCb Domenico Galli, Umberto Marconi and Vincenzo Vagnoni

  13. Long Term: The Proposed INFN Unique Tier-1 RCC • The proposed unique INFN Tier-1 Regional Computing Centre for the 4 LHC experiments doesn’t change LHCb-Italy computing planning. • Since the beginning LHCb-Italy planned indeed to build up a “concentrated” Tier-1, and already in 2001, it will put computing resources in only one site (the Tier-1 prototype at CNAF). • On the contrary, ALICE, ATLAS and CMS had to revise their plan. Now they try to move resources from Tier-1s to Tier-2s, but it is not clear if this scheme will be practicable. INFN Computing for LHCb Domenico Galli, Umberto Marconi and Vincenzo Vagnoni

  14. Final Tier-n Organization in Italy • ATLAS-Italy plan: • Tier-1 stores ESD. Performs reprocessing and first analysis stage (AOD production). No MC production. • Tier-2s store AOD and perform MC production + analysis. • Tier-3s execute analysis. • CMS-Italy plan: • Tier-1 stores ESD and performs collaboration scheduled MC production + reprocessing. • Tier-2++ (Legnaro) performs local requested MC production + reprocessing + analysis. • Tier-2s/Tier-3s produce local requested MC production + analysis. • Tier-2/Tier-3 difference is not functional-based. INFN Computing for LHCb Domenico Galli, Umberto Marconi and Vincenzo Vagnoni

  15. Final Tier-n Organization in Italy (II) • LHCb-Italy plan: • LHCb distributes AOD (not ESD) to Tier-1s. User analyses in Tier-3 will access mainly AOD. • LHCb-Italy believes that in the next years most of manpower will be absorbed by Tier-1 construction. • No pre-existent (reasonable sized) farms in INFN institutes. • Rather than build up possible Tier-2s, it is preferable, for LHCb-Italy, to concentrate on Tier-1. • LHCb-Italy plan to build: • 1 Tier-1; • 9 Tier-3 (one for each institute). INFN Computing for LHCb Domenico Galli, Umberto Marconi and Vincenzo Vagnoni

  16. LHCb-Italy Tier-n Tasks • Tier-1. • MC production ( RAWmc,  ESDmc) + production analysis ( AOD) + MC reprocessing following changes in reconstruction algorithms ( ESDmc). • User analysis (selection task) in collaboration with Tier-3s. • Storage of RAWmc and ESDmc produced in the centre itself. • Storage of all the AOD (real AOD produced at CERN, MC AOD produced in all Tier-1 centres). • Tier-3s. • User analysis (processing task,  DPD) in collaboration with Tier-1. • Interactive analysis of DPD. • Storage of AOD selections. • Storage of DPDs. INFN Computing for LHCb Domenico Galli, Umberto Marconi and Vincenzo Vagnoni

  17. LHCb Requirements for INFN unique Tier-1 • INFN unique Tier-1 must place at LHCb’s disposal the computing resources needed (in terms of CPU power, disk/tape storage, connectivity, etc.), • with the requirements demanded by LHCb (operating system, experiment software, etc.). • Personnel at Tier-1 should include: • Qualified system administrators; • Computer scientist motivated by the interest about computing methods; • Physicists directly involved in analysis, motivated by the scientific results. • Experiments should exert on Tier-1 a strong steering and control action (more like a “board of directors” than a “user council”). INFN Computing for LHCb Domenico Galli, Umberto Marconi and Vincenzo Vagnoni

  18. LHCb Tier-1 Capacity Needs INFN Computing for LHCb Domenico Galli, Umberto Marconi and Vincenzo Vagnoni

  19. LHCb-Italy Required Personnel INFN Computing for LHCb Domenico Galli, Umberto Marconi and Vincenzo Vagnoni

  20. Final LHCb Tier-n Organization in Italy INFN Computing for LHCb Domenico Galli, Umberto Marconi and Vincenzo Vagnoni

  21. RCC Project Committee • February 6, 2001: the INFN President elected a Project Committee for the Regional Computing Centre: • Paolo Capiluppi (CMS, Bologna) • Domenico Galli (LHCb, Bologna) • Alberto Masoni (ALICE, Cagliari) • Mauro Morandin (BaBar, Padova) • Laura Perini (ATLAS, Milano) • Fulvio Ricci (VIRGO, Roma) • Federico Ruggieri (CNAF, Bologna) • Other experts will be involved. INFN Computing for LHCb Domenico Galli, Umberto Marconi and Vincenzo Vagnoni

  22. RCC Preliminary Time Schedule • February 13, 2001: first meeting of the Project Committee. • April 10, 2001: detailed working plan for the experimental phase and general working plan for the executing phase. • July 2001: adjustment of the plan to the results of LHC Computing Review. • End 2001: study of tecnical, economical, and organizational problems and beginning of experimental phase. • End 2002: revisal on the basis of the experiment engagements in MoU. • End 2003: end of the experimental phase. INFN Computing for LHCb Domenico Galli, Umberto Marconi and Vincenzo Vagnoni

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