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TierStore and DTN Distributed Storage in Cambodia

TierStore and DTN Distributed Storage in Cambodia. Michael Demmer. Introduction / Outline. Cambodia and the CIC Project The TierStore / DTN Technology Tier Cambodia Project Plan. Cambodia Overview. Population: ~13 Million Land: ~175,000 sq. km Roughly the size of Oklahoma

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TierStore and DTN Distributed Storage in Cambodia

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  1. TierStore and DTNDistributed Storage in Cambodia Michael Demmer

  2. Introduction / Outline • Cambodia and the CIC Project • The TierStore / DTN Technology • Tier Cambodia Project Plan

  3. Cambodia Overview • Population: ~13 Million • Land: ~175,000 sq. km • Roughly the size of Oklahoma • GDP per capita (2004 est.): ~$2000 • (measured in purchasing power parity) • Comparison: US: ~$40,000, India: ~$3100 • Population below poverty line: 40% (Source: CIA - The World Factbook)

  4. Cambodia Infrastructure • Phones (2002 est.): • ~35,000 land, ~380,000 cell • Internet access (2003 est.): • ~818 hosts, ~30,000 users • Internet costs: • 64k wireless: $55/month • 56k dialup: $150/month • 9.6k mobile: $100-$300/month (Source: CIA - The World Factbook)

  5. Community Information Centers • Asia Foundation project • USAID Supported • 22 centers • (some closing) • Basic Training / Internet Access • All provinces

  6. CIC Internet Access • Varied connectivity based on availability • Broadband @ ~300kbps • Cell-phone based dialup @ 9.6kbps

  7. Introduction / Outline • Cambodia and the CIC Project • The TierStore / DTN Technology • Tier Cambodia Project Plan

  8. Internet DTN Overview • Store-and-forward network • Varied underlying technologies • Novel routing, classes of service, reliability

  9. TierStore Overview • Persistent, replicated, storage using DTN as a transport • Hierarchical storage model • Filesystem interface • Eventually consistent • Application-specific plugins • Email, http, log collection /sub/<id>/<path> WebProxy /objects/<guid> /web/web/mirrors/…/web/forms/… EmailProxy /mail/<user>/inbox /sensors/<field1>/… Object Store SensorBase

  10. Why this approach? • Fundamentally hard and expensive to get reliable network links • Common infrastructure to deal with challenging network environment • Easy app integration • Benefits from local caching, more efficient network usage

  11. Introduction / Outline • Cambodia and the CIC Project • The TierStore / DTN Technology • Tier Cambodia Project Plan

  12. Tier Cambodia: Phase 1 • July 2005 Visit • Tour of centers, meetingswith Asia Foundation • Installed network monitoring software • Packet logger onto 1GB USB drive • Five centers w/ varied connectivity • Obtained traffic logs from web proxy

  13. Early Challenges • Language, timezone • Debugging from the other side of the world • Unexpected issues • ~1 week after we left, windows reinstall erased monitoring software • Funding shortage cut some internet access • Still optimistic…

  14. CIC Traffic analysis • Inefficiency of web-based email: • Yahoo CheckMail avg download 78KB vs. mail spool avg message 12KB • Doesn’t even count images, other URLs

  15. Tier Cambodia: Phase 2 • January 2006 Visit • Prototype TierStore / DTNdeployment • Goals: • Demonstrate viability of the solution • Better access in poorly connected centers • Show cost benefit of asynchronous connectivity, store-and-forward

  16. Results / Conclusions • Stay tuned…

  17. Backup

  18. Total number of visitors Monthly visitors 18000 16000 30000 14000 12000 25000 10000 20000 8000 6000 15000 4000 2000 10000 0 5000 April May June July Aug Sept 0 NGOs Business and Private Sector Government agencies Political parties Feb Dec Oct Apr Aug June Students Other CIC Usage Statistics • Over 500,000 visits since opening the first center in 2003 • ~37,000 users (April-September 2004 Statistics, courtesy of Pauline Tweedie)

  19. Conflict Management • All distributed storage systems must worry about conflicting operations • Intermittency makes this even harder • How to deal with conflicts? • Subscription granularity • Conflict-free naming • “View” splits, app handlers

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