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Causal Logging : Manetho

Causal Logging : Manetho. Rohit C Fernandes 10/25/01. Manetho System Model. Non determinististic events Message Receive Internal event(Kernel call) Creation of a new process Output Commit Stable Storage + Volatile Memory. Manetho properties. Tolerate any number of simultaneous failures

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Causal Logging : Manetho

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  1. Causal Logging : Manetho Rohit C Fernandes 10/25/01

  2. Manetho System Model • Non determinististic events • Message Receive • Internal event(Kernel call) • Creation of a new process • Output Commit • Stable Storage + Volatile Memory

  3. Manetho properties • Tolerate any number of simultaneous failures • Low failure-free overhead • Only failed processes roll back

  4. Example Manetho Execution

  5. Causal Logging : Intuition • Piggyback determinant of non-deterministic event on outgoing messages • Determinant? • Piggyback Antecedence Graphs

  6. Antecedence Graph • Directed acyclic graph • Nodes : State Intervals • Edges : Happened before(immediate)

  7. Antecedence Graph

  8. Receive Node • Two incoming edges • Fields • Receiver ID • Sender ID • Index of created state interval • Unique identifier of message

  9. Internal Event Node • One incoming edge • Fields • Type of event • Replay information

  10. Failure Free Operation • Each process maintains • AG of its current interval • Log that contains data and ID of each message sent • Message Send : Piggyback AG of current state interval

  11. Optimization • Need not send complete AG • Incremental piggybacking • AG(i+1p) is a proper subgraph of AG(ip) • Process q communicates to p max j such that jp is in q’s AG • P sends AG (ip ) - AG (jp )

  12. Information on Stable Storage • Checkpoints • AG (asynchronously) : Need not piggyback part of AG which is in disk • Output commit: Save AG to disk

  13. Incarnation Numbers • Each process starts a new incarnation after recovery • Integer stored in stable storage • Tagged on outgoing messages • Messages from old incarnations discarded

  14. Recovery Protocol • Recover(p,c,INCNUM,S) • Step 1 • INCNUM  INCNUM+1 ; save INCNUM • INCVEC[p] INCNUM • G AG(pc) // stable storage

  15. Recovery Protocol • Step 2 • For all q  S, qp • (INQ,AGQ)remote call at q:GET_AG(p) • GGAGQ • INCVEC[q]INQ • For all q  S, qp • Remote call at q: SEND_INC(p,INCVEC)

  16. Recovery Protocol • Step 3 • mmax j such that pj  G • Recover upto pm • Don’t send out application messages but log them • For receive, request message from sender’s log • Replay internal event

  17. Recovery Example

  18. Available Antecedence Graphs

  19. Application Characteristics

  20. Performance Overhead

  21. Coordinated vs. Uncoordinated

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