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From Shawn Heisey <>
Subject Re: What contributes to disk IO?
Date Wed, 26 Mar 2014 16:26:18 GMT
On 3/25/2014 6:12 PM, Software Dev wrote:
> What are the main contributing factors for Solr Cloud generating a lot
> of disk IO?
> A lot of reads? Writes? Insufficient RAM?
> I would think if there was enough disk cache available for the whole
> index there would be little to no disk IO.

Toke's answer is spot on.

Something additional: In a previous thread, you mentioned optimizing.  
That will generate a lot of disk I/O, most of which is unavoidable.  
Actual disk write I/O is completely unavoidable with an optimize, no 
matter how big your disk cache is.  Unless you have TWICE your index 
size in RAM available for the disk cache, a large percentage of the read 
I/O from an optimize will also hit the disk, because the optimized index 
will push the old index out of the disk cache.  This slows down searches.


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