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From Mike Klaas <>
Subject Re: detected corrupted index / performance improvement
Date Thu, 07 Feb 2008 23:19:26 GMT

On 7-Feb-08, at 2:00 PM, robert engels wrote:

> My point is that commit needs to be used in most applications, and  
> the commit in Lucene is very slow.
> You don't have 2x the IO cost, mainly because only the log file  
> needs to be sync'd.  The index only has to be sync'd eventually, in  
> order to prune the logfile - this can be done in the background,  
> improving the performance of update and commit cycle.
> Also, writing the log file is very efficiently because it is an  
> append/sequential operation. Writing the segment files writes  
> multiple files - essentially causing random access writes.

For large segments, multiple sequentially-written large files should  
perform similarly to one large sequentially-written file.  It is only  
close to random access on the smallest segments (which a sufficiently- 
large flush-by-ram shouldn't produce).


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