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From Shawn Heisey <s...@elyograg.org>
Subject Re: Sending shard requests to all replicas
Date Sat, 27 Jul 2013 22:06:35 GMT
On 7/27/2013 3:33 PM, Isaac Hebsh wrote:
> I have about 40 shards. repFactor=2.
> The cause of slower shards is very interesting, and this is the main
> approach we took.
> Note that in every query, it is another shard which is the slowest. In 20%
> of the queries, the slowest shard takes about 4 times more than the average
> shard qtime.
> While continuing investigation, remember it might be the virtualization /
> storage-access / network / gc /..., so I thought that reducing the effect
> of the slow shards might be a good (temporary or permanent) solution.

Virtualization is not the best approach for Solr.  Assuming you're
dealing with your own hardware and not something based in the cloud like
Amazon, you can get better results by running on bare metal and having
multiple shards per host.

Garbage collection is a very likely source of this problem.

http://wiki.apache.org/solr/SolrPerformanceProblems#GC_pause_problems

> I thought it should be an almost trivial code change (for proving the
> concept). Isn't it?

I have no idea what you're saying/asking here.  Can you clarify?

It seems to me that sending requests to all replicas would just increase
the overall load on the cluster, with no real benefit.

Thanks,
Shawn


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