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Re: 8.4.1 ubuntu karmic slow createdb

From: Andres Freund <andres(at)anarazel(dot)de>
To: pgsql-performance(at)postgresql(dot)org
Cc: Scott Marlowe <scott(dot)marlowe(at)gmail(dot)com>, Michael Clemmons <glassresistor(at)gmail(dot)com>
Subject: Re: 8.4.1 ubuntu karmic slow createdb
Date: 2009-12-12 00:19:38
Message-ID: 200912120119.39272.andres@anarazel.de (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-performance
Hi,

On Saturday 12 December 2009 00:59:13 Scott Marlowe wrote:
> On Fri, Dec 11, 2009 at 3:52 PM, Michael Clemmons
> >  Createdb takes
> > 12secs on my system(9.10 pg8.4 and ext4)  which is impossibly slow for
> > running 200unittests.
> >  Fsync got it to .2secs or so which is blazing but
> > also the speed I expected being used to 8.3 and xfs.  This dev box is my
> > laptop and the data is litterally unimportant and doesn't exist longer
> > than 20sec but Im all about good practices.  Will definately try
> > synchronous commit tonight once Im done working for the day.  I've got
> > some massive copying todo later though so this will probably help in the
> > future as well.
> Yeah, I'd probably resort to fsync off in that circumstance too
> especially if syn commit off didn't help that much.
How should syn commit help with creating databases?

The problem with 8.4 and creating databases is that the number of files 
increased hugely because of the introduction of relation forks.
It probably wouldnt be that hard to copy all files first, then reopen and fsync 
them. Actually that should be a patch doable in an hour or two.

Andres

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