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Message-ID: <54653BBB.5060508@consistentstate.com>
Date: Thu, 13 Nov 2014 16:16:11 -0700
From: CS DBA <cs_dba@consistentstate.com>
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To: pgsql-performance@postgresql.org
Subject: Re: Increased shared_buffer setting = lower hit ratio ?
References: <54653A1E.3050805@consistentstate.com>
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This is on a CentOS 6.5 box running PostgreSQL 9.2


On 11/13/14 4:09 PM, CS DBA wrote:
> 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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