Re: [PERFORM] shared_buffers/effective_cache_size on 96GB server

[Julien Cigar]

On 10/10/2012 09:12, Strahinja Kustudić wrote:
Hi everyone,

Hello,


I have a Postgresql 9.1 dedicated server with 16 cores, 96GB RAM and 
RAID10 15K SCSI drives which is runing Centos 6.2 x64. This server is 
mainly used for inserting/updating large amounts of data via 
copy/insert/update commands, and seldom for running select queries.

Here are the relevant configuration parameters I changed:

shared_buffers = 10GB

Generally going over 4GB for shared_buffers doesn't help.. some of the 
overhead of bgwriter and checkpoints is more or less linear in the size 
of shared_buffers ..

effective_cache_size = 90GB

effective_cache_size should be ~75% of the RAM (if it's a dedicated server)

work_mem = 32MB

with 96GB of RAM I would raise default work_mem to something like 128MB

maintenance_work_mem = 512MB

again, with 96GB of ram you can raise maintenance_work_mem to something 
like 4GB

checkpoint_segments = 64
checkpoint_completion_target = 0.8

My biggest concern are shared_buffers and effective_cache_size, should 
I increase shared_buffers and decrease effective_cache_size? I read 
that values above 10GB for shared_buffers give lower performance, than 
smaller amounts?

free is currently reporting (during the loading of data):

$ free -m
total used free shared buffers cached
Mem: 96730 96418 311 0 71 93120
-/+ buffers/cache: 3227 93502
Swap: 21000 51 20949

So it did a little swapping, but only minor, still I should probably 
decrease shared_buffers so there is no swapping at all.

Thanks in advance,
Strahinja

Julien


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