Message-ID: <42022DA2.3040000@archonet.com>
Date: Thu, 03 Feb 2005 13:56:50 +0000
From: Richard Huxton <dev@archonet.com>
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To: Din Adrian <adrian.din@easynet.ro>
Cc: 'Postgresql Performance' <pgsql-performance@postgresql.org>
Subject: Re: Tunning postgresql on linux (fedora core 3)
References: <opsll8h2shawcxfg@adi> <420202D0.7070602@archonet.com>
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Please CC the mailing list as well as replying to me, so that others can 
help too.

Din Adrian wrote:
> yes I have read this as well ...
> 
> One question about this option:
> fsync = true / false
>  a) I have Raid and UPS - it is safe to turn this off ... (' But be 
> very  aware that any unexpected database shutdown will force you to 
> restore the  database from your last backup.' - from my last backup if 
> the server goes  down ??? why ? just at 'any unexpected database 
> shutdown' ?  ....!!!!!!!!!!!)

Because fsync=true flushes transaction details to disk (the Write Ahead 
Log). That way if (say) the power-supply in your server fails you can 
check the WAL and compare it to the main database files to make sure 
everything is in a known state.

>  b) in docs say that after 7.2 seting this to false does'n turn off the  
> wall ...!? wich option does?

The docs don't say that, as far as I can see. It doesn't make sense to 
turn off the WAL.
--
   Richard Huxton
   Archonet Ltd