Re: Low Performance for big hospital server ..

From: Mark Kirkwood <markir(at)coretech(dot)co(dot)nz>
To: amrit(at)health2(dot)moph(dot)go(dot)th
Cc: PGsql-performance <pgsql-performance(at)postgresql(dot)org>
Subject: Re: Low Performance for big hospital server ..
Date: 2005-01-03 06:19:50
Message-ID: 41D8E406.1090501@coretech.co.nz
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amrit(at)health2(dot)moph(dot)go(dot)th wrote:

>>>max_connections = 160
>>>shared_buffers = 2048 [Total = 2.5 Gb.]
>>>sort_mem = 8192 [Total = 1280 Mb.]
>>>vacuum_mem = 16384
>>>effective_cache_size = 128897 [= 1007 Mb. = 1 Gb. ]
>>>Will it be more suitable for my server than before?
>>>
>>>
>>>
>>>
>>>
>>>
>>I would keep shared_buffers in the 10000->20000 range, as this is
>>allocated *once* into shared memory, so only uses 80->160 Mb in *total*.
>>
>>
>
>You mean that if I increase the share buffer to arround 12000 [160 comnnections
>] , this will not affect the mem. usage ?
>
>
>
shared_buffers = 12000 will use 12000*8192 bytes (i.e about 96Mb). It is
shared, so no matter how many connections you have it will only use 96M.

>>The lower sort_mem will help reduce memory pressure (as this is
>>allocated for every backend connection) and this will help performance -
>>*unless* you have lots of queries that need to sort large datasets. If
>>so, then these will hammer your i/o subsystem, possibly canceling any
>>gain from freeing up more memory. So there is a need to understand what
>>sort of workload you have!
>>
>>
>
>Will the increasing in effective cache size to arround 200000 make a little bit
>improvement ? Do you think so?
>
>
>
I would leave it at the figure you proposed (128897), and monitor your
performance.
(you can always increase it later and see what the effect is).

regards

Mark

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