Skip site navigation (1) Skip section navigation (2)

Re: how to plan for vacuum?

From: Galy Lee <lee(dot)galy(at)oss(dot)ntt(dot)co(dot)jp>
To: pgsql-performance(at)postgresql(dot)org
Cc: jim(at)nasby(dot)net
Subject: Re: how to plan for vacuum?
Date: 2007-01-25 10:29:20
Message-ID: 45B88680.4040500@oss.ntt.co.jp (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-performance

Jim C. Nasby wrote:
> On Wed, Jan 24, 2007 at 02:37:44PM +0900, Galy Lee wrote:
>> 1.  How do we know if autovacuum is enough for my application, or should
>>     I setup a vacuum manually from cron for my application?
> 
> Generally I trust autovac unless there's some tables where it's critical
> that they be vacuumed frequently, such as a queue table or a web session
> table.

So how much can we trust autovac? I think at least the following cases 
can not be covered by autovac now:
  - small but high update tables which are sensitive to garbage
  - very big tables which need a long time to be vacuumed.
  - when we need to adjust the the max_fsm_page

>> 2. How to set the GUC parameters for autovacuum?
>> There are two sets of parameters for autovacuum:
>>     - vacuum threshold and scale factor (500/0.2)
>> ?$B!!  - analyze threshold and scale factor(250/0.1)
>> Is there any guideline to set these parameters?  When does it need to
>> change the default values?
> 
> I find those are generally pretty good starting points; just bear in
> mind that it means 20% dead space.

so what is the principle to set them?
  - keep dead space lower than some disk limit
  - or keep the garbage rate lower than fillfactor
  or any other general principle?


In response to

Responses

pgsql-performance by date

Next:From: Galy LeeDate: 2007-01-25 10:52:50
Subject: Re: [PERFORM] how to plan for vacuum?
Previous:From: Jim C. NasbyDate: 2007-01-25 03:57:42
Subject: Re: [HACKERS] how to plan for vacuum?

pgsql-hackers by date

Next:From: Galy LeeDate: 2007-01-25 10:52:50
Subject: Re: [PERFORM] how to plan for vacuum?
Previous:From: Heikki LinnakangasDate: 2007-01-25 10:21:32
Subject: Re: Piggybacking vacuum I/O

Privacy Policy | About PostgreSQL
Copyright © 1996-2014 The PostgreSQL Global Development Group