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The Tutorial Questions and Lab Projects of Week 5
Tutorial Questions
1. Three computers together provide a replicated service. The manufacturers claim that each
computer has a mean time between failure of five days; a failure typically takes four hours to
fix. What is the availability of the replicated service?
2. What is the consistency issue raised by state transfer?
3. An operation X upon an object O causes O to invoke an operation upon another object O’. It
is now proposed to replicate O but not O’. Explain the difficulty that this raises concerning
invocations upon O’, and suggest a solution.
4. Explain why allowing backups to process read operations leads to sequentially consistent
rather than linearizable executions in a passive replication system.
Lab Projects
The task for Week 5 is to finalise your assignment-1 in lab (with the assistance of your tutor if
necessary).