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From Toke Eskildsen>
Subject Re: Solr Cloud has lower performance with more servers
Date Thu, 09 Oct 2014 13:56:09 GMT
On Thu, 2014-10-09 at 15:06 +0200, Yannick wrote:

> I created a group of 2 Solr servers with a load-balancer in front
> (Haproxy). I have a batch client that sends requests (read-only)
> continuously to the load-balancer. The problem is: the performance is
> slower with 2 servers than it is with a single server (still via the
> load-balancer, with the second server down, so it's not the
> load-balancer itself causing the slowdown).

(speculating a lot here:)

Is another job updating the indexes while you are batch-searching?
If so, the slowdown could be explained by the servers disk caches being
flushed by the indexing job. When a request arrives some cache is
reclaimed, but is will be a battle between the update and the search
jobs. With more machines, there will be fewer request/machine, so the
search-cache has a lower chance of being used again before it is
reclaimed by the updater.

Still, worse performance for 2 machines sounds pretty bad.

- Toke Eskildsen, State and University Library, Denmark

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