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From Mike Klaas <>
Subject Re: Solr Capabilities/Limitations
Date Tue, 01 Jul 2008 21:44:31 GMT
On 1-Jul-08, at 8:37 AM, Willie Wong wrote:

> I need to be able to search through terabytes of existing data.   
> Documents
> may vary in size from 10 MB to 20 KB in size.  Also at some point I’ll
> also need to feed in approximately approximately 1-5 million new  
> documents
> a day.

This depends greatly on what kind of searching you want to do, and  
what are the desired response times.  I'm using Solr to full-text  
search about 10 TB of data at the moment.  Response times are around  
~1s including dynamic snippet generation.  The queries themselves are  
relatively complicated by lucene standards, including a custom word- 
proximity boosting query and link-analysis factors.

Of course, this is distributed over dozens of machines, and is a  
mostly static index.  There are about 10million docs per server.

> Has anyone used Solr to conduct searches over terabytes of data?  If  
> so,
> are there any configuration parameters I should pay particular  
> attention
> to such jvm size, mergeFactor etc?

JVM size will depend mostly on your sorting/faceting requirements.   
Just remember to leave gobs of memory for the OS disk cache.  Memory  
is key to serving large indices (consequently, things won't be fast  
until a decent amount of warming up is done).  mergeFactor?  You  
should only be searching optimized indices of this size, so it isn't  
terribly relevant.  The daily new docs should probably be added in  
their own index, which is then searched in parallel with the existing  

> Is there a limit to the number of shards Solr is capable of?  I don’t
> think there’s any way I can do this without some sort of distributed
> search.

Not really, though you will want to move to a 2-level hierarchy  
eventually.  I can't speak for the distributed search implementation  
in trunk (we built our own before this was available), but it should  
be exactly what you need.

> I’ve read that solr indexes can go into the millions if not billions  
> of
> documents… however at what point do the index size become  
> impractical – I
> know this is a bit open ended, but I guess does Solr have a limit to  
> the
> number of documents that can be in a single index?

Depends on query composition and document size.  But for web docs,  
about 10m seems practical.

> Has anyone looked into any of these other search engines and are  
> there any
> other search engines that would be better suited such as Fast or  
> Automomy:

I haven't, but it should be possible to build a system based on those  
engines.  For a system this size, the distributed architecture will be  
more important than the underlying index engine (though it sure helps  
to use an engine as optimized as lucene).

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