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From "Ganesh" <>
Subject Re: Sharding Techniques
Date Wed, 11 May 2011 05:09:38 GMT

We also use similar kind of technique, breaking indexes in to smaller and search using ParallelMultiSearcher.
We have to do incremental indexing and the records older than 6 months or 1 year (based on
ageout setting) should be deleted. Having multiple small indexes is really fast in terms of

Since you guys mentioned about keeping single large index. Search time woule be faster but
the indexing and index optimization will take more time. How you are handling it in case of
incremental indexing. If we keep the indexes size to 100+ GB then each file size (fdt, fdx
etc) would in GB's. Small addition or deletion to the file will not cause more IO as it has
to skip those bytes and write it at the end of file.   


----- Original Message ----- 
From: "Burton-West, Tom" <>
To: <>
Sent: Tuesday, May 10, 2011 9:46 PM
Subject: RE: Sharding Techniques

Hi Samar,

>>Normal queries go fine under 500 ms but when people start searching
>>"anything" some queries take up to > 100 seconds. Don't you think
>>distributing smaller indexes on different machines would reduce the average
>>.search time. (Although I have a feeling that search time for smaller queries
>>may be slightly increased)

What are the characteristics of your slow queries?  Can you give examples?   Are the slow
queries always slow or only under heavy load?   What the bottleneck is and whether splitting
into smaller indexes would help depends on just what your bottleneck is. It's not clear that
your index is large enough that the size of the index is causing your bottleneck.

We run indexes of about 350GB with average response times under 200ms and 99th percentile
reponse times of under 2 seconds. (We have a very low qps rate however).


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