1. Torrent base of software distribution by ALICE at RDIG V.V. Kotlyar (IHEP, Protvino), E.A. Ryabinkin (RRC-KI, Moscow), I.A. Tkachenko (RRC-KI, Moscow), G.S. Shabratova (LHEP JINR, Dubna), A.K. Zarochentsev (St. Petersburg State University, St. Petersburg) 5 th International Conference GRID‘2012 "Distributed Computing and Grid-technologies in Science and Education“, 16-21 July, 2012, Dubna, Russia

2. AliEn & ALICE Grid AliEn: ‘Alice Environment’ – Central Services at CERN Task Queue, Job & File Catalog Software management (build & deployment) – VO box site-specific operations Job Agent submission Software deployment Resource monitoring – Grid Monitoring with MonaALisa – Data Management AliEn File Catalog Grid-Enabled XRootD SEs This talk

3. Types of Software Deployment Traditional AliTorrent Central Management: -Additional AliEn torrent store -Catalogue, seeder & tracker Central Management: -Routine software builds -Catalogue& store in AliEn Site SW operation: -Job request SW from VO box service -VO box PackMan service pulls SW -SW deployed on shred area -WNs read SW from shared area Site SW operation: -VO box is not involved -Jobs pull SW from: alitorrent.cern.ch speeder local peers other sides as available -though typically behind a FW Shared SW area: -Resource bottleneck -Single point of failure -Can require active repairs per site Resolves: -Bottleneck & single point failures -Site level maintenance of shared area

4. Basic Torrent details File chunks contain hashes of original file to Provide Data integrity Tracker: map of seeders:files Seeders: have & serve file Leeches: pull & serve file chunks

5. AliTorrent Details Torrent Features – Distributed Hash Tables Decentralized seeder lookup – seeders are trackers – Peer Exchange Local peer information is propagated by seeders – Local Peer Discovery Multicast to discover peers on same network ALICE/AliEn Features – Total software download is 300--‐400MB – Enabled per site (VO box) with AliEn LDAP flag name=,ou=CE,ou=Services,ou=,ou=Sites,o=alice,dc=cern,dc=ch installMethod=Torrent

6. AliTorrent as an opportunity AliTorrent use in AliEn – Reduces problems associated with SW deployment – Simplifies site operations by removing a VO Box service *Does not eliminate VO box model from ALICE Grid * Does eliminate site-specific VO box requirement Elimination of site--‐specific VO box allows for remote use of other Grid resources: exmp-> OSG

7. AliTorrent ALICE torrent-based software distribution links: ( see at http://alitorrent.cern.ch/ ) – Available software packages Available software packages – Seeder statistics Seeder statistics – Seeder network traffic monitoring Seeder network traffic monitoring – Stand-alone torrent clients Stand-alone torrent clients

8. Towards production operations Site policy caution: – limits can be broad – has hampered wider use ALICE Experience: – initial distrust turns into recognition of approach’s merit: Stable running at CERN, 2 T1s and a few T2s (including RRC-KI and IHEP) – simplifies site operations BitTorrent

9. Summary Software deployment on shared area – Bottleneck & site-level single point failure – site-level SW corruption requires admin intervention Torrent model AliTorrent – Removes bottleneck & site-level single point of failure – Eliminates a site service & reduces site management – Performance capabilities meets typical ALICE workflow & site requirements Eliminates requirement for site‐specific VO box AliTorrent is a site-friendly tool for opportunistic (or general) use – don’t ask the site to “do” something -> install or manage a service – ask the site to “not do” something -> Block Torrent use. Talk has been prepared on the base: -Report of C. Grigoras at ALICE T1/T2 workshop, Karlsruhe, Germany, January, 2012 -Report of R.J. Porter et al at CHEP 2912, New York, USA, May, 2012