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From Chris Hostetter <>
Subject Re: The mechanism of data replciation in Solr?
Date Wed, 05 Sep 2007 17:56:01 GMT
: snapshot. This technique has these advantages: Can keep multiple
: snapshots on each host without the need to keep multiple copies of
: index files that have not changed. File copying from master to slave

: Why do hard links make file copying between master and slave fast?
: Thanks. Best Regards.

bullets 2 and 3 build off of bullet 1 ... the Lucene file format is 
desigend such that files are only ever added, appended to, or deleted -- 
there is never in rewriting of existing bytes in a file.  so having 
hardlinks to the orriginal files in the snapshot directories on both 
the master/slave means that the rsync operation of a new snapshot only 
needs to send the new data, not diffs or full contents of existing files.


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