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From Shawn Heisey <>
Subject Re: shards per disk
Date Tue, 20 Jan 2015 16:22:22 GMT
On 1/20/2015 7:45 AM, Nimrod Cohen wrote:
> All shards are on the same system each one use different port.
> Data size is about 1T, memory is 192G.

If Solr has to actually go to the disk to satisfy a query, it's going to
be slow.  This will always be true, no matter how many disks you use. 
In terms of performance, disks are like molasses or a glacier compared
to RAM.  Even an SSD is a lot slower.

Solr performance is good when all of the data that a query needs is
sitting in RAM already, cached by the operating system using memory that
is not allocated to programs.  192GB of RAM is nowhere near enough to
assure good performance if the Solr indexes are 1TB in size.  I would
bet that this is true even if you put the indexes on SSD instead of
spinning magnetic drives ... although performance would be better with SSD.

You should *not* run multiple Solr instances per machine.  All of your
index cores should be handled by one instance.  Running multiple
instances is a waste of resources, especially memory, which as already
discussed is extremely precious when dealing with a large index.


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