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15 november 8th 2012 spring 2013 if a replica is

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Unformatted text preview: iden4ty of chunks no longer present •  Erase metadata for these chunks –  Chunk server free to delete its replica of such chunks L24.13 November 8th, 2012 CS480 Principles of Data Management Spring 2013 Stale chunks and issues Spring 2013 •  Master maintains a chunk version number for each chunk –  AND misses muta4ons to the chunk –  The chunk replica becomes stale –  Dis4nguish between stale and up ­to ­date chunks •  Working with a stale replica causes problems with: •  When master grants a new lease on chunk –  Increase version number –  Inform replicas –  Record new version persistently –  Correctness –  Consistency L24.15 November 8th, 2012 Spring 2013 If a replica is unavailable its version number will not be advanced Occurs BEFORE any client can write to chunk November 8th, 2012 CS480 Principles of Data Management L24.16 Spring 2013 Additional safeguards against stale replicas •  Include chunk version number •  When a chunk server restarts, it reports to the Master with the following: –  When client requests chunk...
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