Matt W. Benjamin wrote:
> Ok, sure.  But I believe what you are describing is not invalidation, but 
> rather replacement.  It's not incorrect to use "invalidate" referring to 
> "data."  This precisely means (some specialization of, such as a message 
> indicating) the data as known is not valid, not that replacement data is 
> delivered.  As you state, XCB has operations that replace metadata, but (as 
> with the traditional AFS callback) only invalidate data.  
XCB has the ability to replace or update metadata.  It also has the
ability to "validate" cached data.  A callback that indicates that
between DV=N and DV=N+1 the following set of data ranges were altered
also asserts that if the cache contains data in other ranges tagged with
DV=N, it is now DV=N+1.  data within the invalidated ranges must be
purged.  That is the important gain that XCB messages sent as a result
of StoreData and MiniData operations provide.

Jeffrey Altman




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