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Date: Thu, 13 Nov 2014 16:09:18 -0700
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To: pgsql-performance@postgresql.org
Subject: Increased shared_buffer setting = lower hit ratio ?
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All;

We have a large db server with 128GB of ram running complex functions.

with the server set to have the following we were seeing a somewhat low 
hit ratio and lots of temp buffers

shared_buffers = 18GB
work_mem = 75MB
effective_cache_size = 105GB
checkpoint_segments = 128


when we increased the values to these not only did the hit ratio drop 
but query times are now longer as well:


shared_buffers = 28GB
work_mem = 150MB
effective_cache_size = 105GB
checkpoint_segments = 256

This does not seem to make sense to me, anyone have any thoughts on why 
more memory resources would cause worse performance?

Thanks in advance



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