Hi,
I have not tried all the settings on the big database but yeah I have tried most of the settings and I am not seeing any performance improvement. Rather I would say that there was a performance degradation in my case when I used some of the settings used for small database (like decreasing shared_buffers, checkpoint_segments etc). I am trying to change these parameters one by one and then see how things are getting affected.
Regards, Vinita Bansal
From: Scott Marlowe <[EMAIL PROTECTED]> To: vinita bansal <[EMAIL PROTECTED]> CC: pgsql-general@postgresql.org Subject: Re: [GENERAL] importance of bgwriter_percent Date: Fri, 01 Apr 2005 09:43:38 -0600
On Fri, 2005-04-01 at 00:36, vinita bansal wrote: > Hi, > > I have a 64 bit Linux box with 64GB RAM and 450GB HDD. I am running a > benchmark on database of size 40GB using the following settings: > - data=writeback
You might want to read this post about ext3 with writeback:
http://archives.postgresql.org/pgsql-general/2005-01/msg00830.php
> - Moved wal logs to seperate partition
> - settings in postgresql.conf:
> shared_buffers = 100000
> work_mem = 100000
> maintenance_work_mem = 100000
> max_fsm_pages = 200000
> bgwriter_percent = 2
> bgwriter_maxpages = 100
> fsync = false
> wal_buffers = 64
> checkpoint_segments = 2048
> checkpoint_timeout = 3600
> effective_cache_size = 1840000
> random_page_cost = 2
> geqo_threshold = 25
> geqo_effort = 1
> stats_start_collector = false
> stats_command_string = false
> stats_row_level = false
> add_missing_from = false
>
> I am not getting good performance here as I get when I am working on a small
> database of size 1GB with the following settings :
> shared_buffers = 3000
> checkpoint_segments = 256
> checkpoint_timeout= 1800
> effective_cache_size= 250000
> Rest all settings are the same as above.
What is the difference in performance on the big database if you use the settings from the small setup instead of the ones you're using now? Have you tried starting there and increasing each setting some incremental amount to gauge the increase in performance you get from the changes? Sometimes certain settings that you think will speed up the database will actually slow it down, and without some kind of empirical testing, you really don't know if the new setting is really "better" or not.
I'm not familiar enough with the new bgwriter stuff yet to offer any real advice on tuning its parameters.
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