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From Scott Ganyo <>
Subject Re: Lucene Benchmarks and Information
Date Fri, 20 Dec 2002 18:58:02 GMT
FYI: The best thing I've found for both increasing speed and reducing 
file handles is to use an IndexWriter on a RamDirectory for indexing and 
then use FileWriter.addIndexes() to write the result to disk.  This is 
subject to the amount of memory you have available, of course...


Armbrust, Daniel C. wrote:

>I've been running some scalability tests on Lucene over the past couple of weeks.  While
there may be some flaws with some of my methods, I think they will be useful for people that
want an idea as to how Lucene will scale.  If anyone has any questions about what I did, or
wants clarifications on something, I'll be happy to provide them.
>I'll start by filling out the form
>      Hardware Environment
>    * Dedicated machine for indexing: yes
>    * CPU: 1 2.53 GHz Pentium 4
>    * RAM: Self-explanatory
>    * Drive configuration: 100 GB 7200 RPM IDE, 80 GB 7200 RPM IDE
>      Software environment
>    * Java Version: java version "1.3.1"
>	Java(TM) 2 Runtime Environment, Standard Edition (build 1.3.1)
>	Classic VM (build 1.3.1, J2RE 1.3.1 IBM Windows 32 build cn131-20020403 (JIT enabled:
>    * OS Version: Win XP SP1
>    * Location of index: Local File Systems
>      Lucene indexing variables
>    * Number of source documents: 43,779,000
>    * Total filesize of source documents: ~350 GB -- never stored (documents were randomly
>    * Average filesize of source documents: 8 KB
>    * Source documents storage location: Generated while indexing, never written to disk
>    * File type of source documents: text
>    * Parser(s) used, if any: None
>    * Analyzer(s) used: Standard Analyzer
>    * Number of fields per document: 2
>    * Type of fields: text, Unstored
>    * Index persistence: FSDirectory
>      Figures
>    * Time taken (in ms/s as an average of at least 3 indexing runs): See notes below
>    * Time taken / 1000 docs indexed: 6.5 seconds/1000, not counting optimization time.
 15 seconds/1000 when optimizing every 100,000 documents, and building an index to ~ 5 million
documents.  Above 5 million documents, optimization took too much time.  See notes below.
>    * Memory consumption: ~ 200 mb
>   *  Index Size: 70.7 GB
>      Notes
>    * Notes: The documents were randomly generated on the fly as part of the indexing
process from a list of ~100,000 words, who's average length was 7.   The documents had 3 words
in the title, and 500 words in the body.
>While I was trying to build this index, the biggest limitation of Lucene that I ran into
was optimization.  Optimization kills the indexers performance when you get between 3-5 million
documents in an index.  On my Windows XP box, I had to reoptimize every 100,000 documents
to keep from running out of file handles.  While I could build a 5 million document index
in 24 hours... I could only add about another million over the next 24 hours due to the pain
of the optimizer recopying the entire index over and over again (about 10 GB at this point),
and it would only get worse from there.  So, to build this large of an index, I built several
~ 5 million document indexes, and then merged them at the end into a single index.  The second
issue (though not really a problem) was that you have to have at least double the disk space
available to build the index as you need when you are done.  I could have kept building the
index bigger, but I ran out of disk space.  
>When I was done building indexes, I ran some query's against them to see how the search
performance varied with the size of the index.  Following are my results for various size
>Index Size (GB) 		MS per query
>4.53				83
>7.92				83
>10				89
>12.7				112
>52.5				694
>70.7				944
>These numbers are an average of 3 runs of 500 randomly generated queries being tossed
at the index (single threaded) on the same hardware that built the index.  The queries were
randomly generated (about 50 % of the queries had 0 results, 50% had 1 or more results) 
>I was happy to see that these numbers make a nice linear plot (attached).  I'm not sure
what other comments to add here, other to thank the authors of Lucene for their great design
and implementation of Lucene.
>If anyone has anything else they would like me to test on this index before I dump it...
Speak up quick, I have to pull out one of the hard drives this weekend to pass it on to its
real owner.
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