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Message Posted: Fri, 18 Dec 2015 @ 19:52:51 GMT


     
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Subj:   Re: Master Index and Cylinder Index
 
From:   Walter, Todd

The Master Index is stored in internal PDE memory. It does not exist as a disk structure, is created at system startup and is maintained only in memory (no writes for changes).

The cylinder indexes are stored as the first part of each cylinder on disk (hasn't actually been a cylinder for a long time, now just a file system allocation unit). The CIs are cached in FsgCache and are managed there like other file system structures using the MRU algorithm for deciding what stays in cache. If changed, changes are logged in the WAL log and when it is time to flush from the cache they are also written back to disk to maintain the persistent version there.



     
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