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From Apache Wiki <wikidi...@apache.org>
Subject [Hadoop Wiki] Update of "BookieRecoveryPage" by FlavioJunqueira
Date Fri, 02 Oct 2009 11:40:53 GMT
Dear Wiki user,

You have subscribed to a wiki page or wiki category on "Hadoop Wiki" for change notification.

The "BookieRecoveryPage" page has been changed by FlavioJunqueira:
http://wiki.apache.org/hadoop/BookieRecoveryPage?action=diff&rev1=3&rev2=4

  
  Such a recovery tool can run either as a separate client or directly in a bookie. The advantage
of implementing recovery on the client side is simplicity: we can just leverage the client
implementation to read entries and write to the new bookie. Performing such a task in a client,
however, may lead to an inefficient utilization of network bandwidth. For an efficient utilization
of network bandwidth, it is best to copy entries directly. 
  
+ After executing such a recovery procedure, one expects to have valid copies of the entries
in the new bookie(s). To validate entries, a user needs the secret that was used to write
to the ledger. It becomes a concern then to use such secrets if one is to perform recovery
of ledgers in batches, as such a user needs to know all secrets of all ledgers to be recovered.
We can, however, separate concerns and make copying separate from validation. That is, we
could have two separate tools, one for copying and another for data integrity validation.
 
+ 
  
  == Design choices ==
  

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