chap-06 - Consistency and Replication Chapter 6 Object...

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Consistency and Replication Chapter 6
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Object Replication (1) Organization of a distributed remote object shared by two different clients.
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Object Replication (2) a) A remote object capable of handling concurrent invocations on its own. b) A remote object for which an object adapter is required to handle concurrent invocations
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Object Replication (3) a) A distributed system for replication-aware distributed objects. b) A distributed system responsible for replica management
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Data-Centric Consistency Models The general organization of a logical data store, physically distributed and replicated across multiple processes.
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Strict Consistency Behavior of two processes, operating on the same data item. A strictly consistent store. A store that is not strictly consistent.
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Linearizability and Sequential Consistency (1) a) A sequentially consistent data store. b) A data store that is not sequentially consistent.
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Linearizability and Sequential Consistency (2) Three concurrently executing processes. z = 1; print (x, y); y = 1; print (x, z); x = 1; print ( y, z); Process P3 Process P2 Process P1
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Linearizability and Sequential Consistency (3) Four valid execution sequences for the processes of the previous slide. The vertical axis is time. y = 1; x = 1; z = 1; print (x, z); print (y, z); print (x, y); Prints: 111111 Signature: 111111 (d) y = 1; z = 1; print (x, y); print (x, z); x = 1; print (y, z); Prints: 010111 Signature: 110101 (c) x = 1; y = 1; print (x,z); print(y, z); z = 1; print (x, y); Prints: 101011 Signature: 101011 (b) x = 1; print ((y, z); y = 1; print (x, z); z = 1; print (x, y); Prints: 001011 Signature: 001011 (a)
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Casual Consistency (1) Necessary condition: Writes that are potentially casually related must be seen by all processes in the same order. Concurrent writes may be seen in a different order on different machines.
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Casual Consistency (2) This sequence is allowed with a casually-consistent store, but not with sequentially or strictly consistent store.
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Casual Consistency (3) a) A violation of a casually-consistent store. b) A correct sequence of events in a casually-consistent store.
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FIFO Consistency (1) Necessary Condition: Writes done by a single process are seen by all other processes in the order in which they were issued, but writes from different processes may be seen in a different order by different processes.
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FIFO Consistency (2) A valid sequence of events of FIFO consistency
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This note was uploaded on 03/24/2009 for the course CSE 403 taught by Professor Tushassir during the Spring '09 term at University of Dhaka.

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chap-06 - Consistency and Replication Chapter 6 Object...

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