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Re: FSM settings -- how to tell if they are working?

From: Robert Treat <xzilla(at)users(dot)sourceforge(dot)net>
To: Jeff Boes <jboes(at)nexcerpt(dot)com>
Cc: pgsql-admin(at)postgresql(dot)org
Subject: Re: FSM settings -- how to tell if they are working?
Date: 2003-01-30 16:02:25
Message-ID: 1043942545.2644.43.camel@camel (view raw or flat)
Thread:
Lists: pgsql-admin
On Mon, 2003-01-27 at 13:25, Jeff Boes wrote:
> We have both test and production databases, about 10 GB total in each.
> Recently, I learned about "max_fsm_pages" and "max_fsm_relations". To get
> a feel for what changing these settings would do to our production
> database, I set the following values in the "test" database:
> 
> max_fsm_relations = 100
> max_fsm_pages = 350000
> 
> but left the production server alone. How can I tell if these new
> settings are having any effect?  How can I determine if these numbers are
> the best choices?
> 
> We perform full vacuums on each of 103 tables every night (including many
> very small tables, which exist only to provide references for foreign
> keys -- "code tables").
> 

I think you would have to parse your vacuum verbose output to determine
if disk usage is growing in accordance to how your data is coming in. 
You might also be able to simply track the file sizes on disk in your
data directories to determine if any particular table is growing out of
control. 

I will say this, you max_fsm_relations is set to low. Right now your
telling it to only keep track of 100 relations, but your vacuuming 103
tables, not to mention system tables as well. You should probably bump
this up to at least 200, for a more specific # search the archives,
there is a query that can tell you a good number to put this at. 

Robert Treat



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