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Dept. of Computer Science & Engineering, CUHK Performance and Effectiveness Analysis of Checkpointing in Mobile Environments Chen Xinyu 2003-01-22
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u Introduction u Mobile Environment – Wireless CORBA u Performance and Effectiveness Analysis of Checkpointing u Conclusions and Future Work Outline
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Introduction u Mobile Computing u Permanent failures Physical damage u Transient failures Mobile hosts Wireless links Environmental conditions
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Checkpointing and Rollback Recovery u Checkpoint the saved program’s states during failure-free execution u Repair brings the failed device back to normal operation u Rollback reloads the program’s states saved at the most recent checkpoint u Recovery the reprocessing of the program, starting from the most recent checkpoint, applying the logged messages and until the point just before the failure
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Wireless CORBA Architecture Visited Domain Home Domain Terminal Domain Access Bridge Static Host Terminal Bridge GIOP Tunnel ab 1 ab 2 mh 1 GTP Messages
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Wireless CORBA Architecture Visited Domain ab 1 ab 2 Access Bridge Static Host Home Domain Home Location Agent Terminal Domain Terminal Bridge GIOP Tunnel mh 1 Terminal Domain Terminal Bridge GIOP Tunnel GIOP Tunnel mh 1 Terminal Domain Terminal Bridge GIOP Tunnel mh 1 Terminal Domain Terminal Bridge Access Bridge
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u Introduction u Mobile Environment – Wireless CORBA u Performance and Effectiveness Analysis of Checkpointing u Conclusions and Future Work Outline
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Program’s Termination Condition u A program is successfully terminated if it receives N computational messages continuously
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Assumptions u Failure occurrence, message arrival and handoff event homogeneous Poisson process with parameter, and respectively u Failures do not occur when the program is in the repair or rollback process u A failure is detected as soon as it occurs
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Execution without Checkpointing RY0Y0 X0X0 R F1F1 H1H1 Z0Z0 0 t FjFj HkHk m j (1)m j (N)m 1 (n 1 )m 0 (N) X(N) RepairHandoff HH
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Conditional Execution Time without checkpointing
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LST without checkpointing
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LST and Expectation of Program Execution Time
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Bounded Situations u Without handoff u Without handoff and failure
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Execution with Equi-number Checkpointing CiCi R+C Y i (0) X i (0) R+C F i (1) H i (1) Z i (0) 0 t F i (j) H i (k) m ij (1)m ij (a)m i1 (n i1 )m i0 (a) X i (N,a) Repair + RollbackHandoff C i-1 Checkpointing HHCC
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Conditional Execution Time & LST with Checkpointing
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LST and Expectation of Program Execution Time
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Average Effectiveness u Effective interval: a program produces useful work towards its completion u Wasted interval: Repair and rollback Handoff Checkpoint creation Wasted Computation u Average Effectiveness: how much of the time an MH is in effective interval during an execution
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Optimal Checkpointing Interval
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Beneficial Condition
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Equi-number Checkpointing u Equi-number checkpointing with respect to message number Message number in each checkpointing interval is not changed u Equi-number checkpointing with respect to checkpoint number Checkpoint number is not changed
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Equi-number Checkpointing with respect to Checkpoint Number
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Equi-number Checkpointing with respect to Message Number
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Comparison Between Checkpointing and Without Checkpointing
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Average Effectiveness vs. Message Arrival Rate and Handoff Rate
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Conclusions u Introduce an equi-number checkpoiting strategy u Derive LST and expectation of program execution time u Derive average effectiveness u Derive optimal checkpointing interval u Identify the beneficial condition
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Future Work u Analytical model Message queuing effect during repair and recovery General event distributions u Fault tolerance in ad hoc network Without infrastructure support Self-organizing and adaptive
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Thank You
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