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Re: Freebsd vs linux and hardware question

From: Dror Matalon <dror(at)zapatec(dot)com>
To: Aditya <aditya(at)grot(dot)org>
Cc: Josh Berkus <josh(at)agliodbs(dot)com>, sfpug(at)postgresql(dot)org
Subject: Re: Freebsd vs linux and hardware question
Date: 2003-09-22 17:57:59
Message-ID: 20030922175759.GV97268@rlx11.zapatec.com (view raw or flat)
Thread:
Lists: sfpug
On Mon, Sep 22, 2003 at 10:42:14AM -0700, Aditya wrote:
> On Mon, Sep 22, 2003 at 10:24:29AM -0700, Josh Berkus wrote:
> > Dror,
> > 
> > > But actually one of the big problems was solved when we ran VACUUM FULL
> > > on a problematic table. It shrank from 100 Megs to 6 Megs which on a
> > > local disk isn't as big a problem as on a NAS.
> > >
> > > We're also now running VACUUM ANALYZE on the table every five minutes
> > > instead of once a day and that helps too.
> > 
> > What is your setting for max_fsm_pages?   Have you compared it against the 
> > results of logged VACUUM VERBOSE?  And I'd be surprised if running VACUUM 
> > ANALYZE ever 5 minutes is necessary ... VACUUM should do, with ANAYLZE maybe 
> > once a day, unless your users are big on changing a large % of rows at once.
> 
> these are the defaults in the config that we're using:
> 
> #max_fsm_relations = 100    # min 10, fsm is free space map
> #max_fsm_pages = 10000      # min 1000, fsm is free space map
> 
> FWIW, there are several thousand rows that get updated every few minutes.
> 
> I'll let Dror answer as to why VACUUM ANALYZE vs. VACUUM alone.

When I run VACUUM every 5 minutes it takes 10 - 20 seconds to finish on
the average. Doesn't seem like the ANALYZE makes a big difference,
although I haven't tested that too carefully.
When I ran it every 10 minutes it took 30 - 40 seconds to finish. I'd
rather run it more often since it seems like it really affects response
time.

> 
> > Finally, what about REINDEX?

I've run REINDEX once. My understanding is that you don't need to run it
on a continous basis (after all shouldn't the tree balance itself on
it's one?). Am I wrong with that?

> 
> Because we have to remove all those addl. deleted/updated rows...
> 
> Aditya

-- 
Dror Matalon, President
Zapatec Inc 
1700 MLK Way
Berkeley, CA 94709
http://www.zapatec.com

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Subject: Re: Freebsd vs linux and hardware question
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