Re: freebsd/softupdates for data dir

From: Mark Kirkwood <markir(at)paradise(dot)net(dot)nz>
To: Miguel <mmiranda(at)123(dot)com(dot)sv>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: freebsd/softupdates for data dir
Date: 2006-04-04 02:10:25
Message-ID: 4431D591.30500@paradise.net.nz
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Miguel wrote:
> Hi, reading the archives i cant find a clear answer about softupdates in
> freebsd, is it recommended to enable it for the data directory?
>

There is a pretty good article about softupdates and journelling here:

http://www.usenix.org/publications/library/proceedings/usenix2000/general/full_papers/seltzer/seltzer_html/index.html

and in the freebsd docs here:

http://www.freebsd.org/doc/handbook/configtuning-disk.html

Postgres does not do a lot of file meta-data operations (unless you do a
*lot* of CREATE/DROP INDEX/TABLE/DATABASE), so the performance gains
associated with softupdates will probably be minimal.

I've always left them on, and never had any issues...(even after
unscheduled power loss - which happened here yesterday). As I understand
it, the softupdate code reorders *metadata* operations, and does not
alter data operations - so the effect of fysnc(2) on a preexisting file
is not changed by softupdates being on or off.

Cheers

Mark

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