From: Jim C. Nasby <decibel@decibel.org>
To: Heikki Linnakangas <heikki@enterprisedb.com>
Cc: Dimitri <dimitrik.fr@gmail.com>
Cc: PostgreSQL Performance <pgsql-performance@postgresql.org>
Subject: Re: Filesystem Direct I/O and WAL sync option
Date: Mon, 9 Jul 2007 15:32:20 -0500
Message-ID: <20070709203220.GO39272@nasby.net> (raw)
In-Reply-To: <468A65F5.8020800@enterprisedb.com>
References: <5482c80a0707030754o740c82b6s4598dc668720d014@mail.gmail.com>
<468A65F5.8020800@enterprisedb.com>
On Tue, Jul 03, 2007 at 04:06:29PM +0100, Heikki Linnakangas wrote:
> Dimitri wrote:
> >I'm very curious to know if we may expect or guarantee any data
> >consistency with WAL sync=OFF but using file system mounted in Direct
> >I/O mode (means every write() system call called by PG really writes
> >to disk before return)...
>
> You'd have to turn that mode on on the data drives as well to get
> consistency, because fsync=off disables checkpoint fsyncs of the data
> files as well.
BTW, it might be worth trying the different wal_sync_methods. IIRC,
Jonah's seen some good results from open_datasync.
--
Jim Nasby decibel@decibel.org
EnterpriseDB http://enterprisedb.com 512.569.9461 (cell)
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To: pgsql-performance@postgresql.org
Cc: decibel@decibel.org, heikki@enterprisedb.com, dimitrik.fr@gmail.com
Subject: Re: Filesystem Direct I/O and WAL sync option
In-Reply-To: <20070709203220.GO39272@nasby.net>
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