Received: from localhost (maia-3.hub.org [200.46.204.184]) by postgresql.org (Postfix) with ESMTP id 3273A9FBBBB for ; Mon, 9 Jul 2007 17:32:41 -0300 (ADT) Received: from postgresql.org ([200.46.204.71]) by localhost (mx1.hub.org [200.46.204.184]) (amavisd-maia, port 10024) with ESMTP id 94631-01 for ; Mon, 9 Jul 2007 17:32:21 -0300 (ADT) X-Greylist: from auto-whitelisted by SQLgrey-1.7.5 Received: from noel.decibel.org (noel.decibel.org [67.100.216.10]) by postgresql.org (Postfix) with ESMTP id B8E0F9FBCD0 for ; Mon, 9 Jul 2007 17:32:25 -0300 (ADT) Received: by noel.decibel.org (Postfix, from userid 1001) id 77C0556442; Mon, 9 Jul 2007 15:32:24 -0500 (CDT) Received: (hashcash-sendmail, from uid 1001); Mon, 9 Jul 2007 15:32:21 -0500 Date: Mon, 9 Jul 2007 15:32:20 -0500 From: "Jim C. Nasby" To: Heikki Linnakangas Cc: Dimitri , PostgreSQL Performance Subject: Re: Filesystem Direct I/O and WAL sync option Message-ID: <20070709203220.GO39272@nasby.net> References: <5482c80a0707030754o740c82b6s4598dc668720d014@mail.gmail.com> <468A65F5.8020800@enterprisedb.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="EgVrEAR5UttbsTXg" Content-Disposition: inline In-Reply-To: <468A65F5.8020800@enterprisedb.com> X-Operating-System: FreeBSD 6.1-RELEASE-p10 amd64 X-Distributed: Join the Effort! http://www.distributed.net User-Agent: Mutt/1.5.13 (2006-08-11) X-Hashcash: 1:20:070709:heikki@enterprisedb.com::yyxZSXQK80qRX2JR:00000000000000 000000000000000000000000DASl X-Hashcash: 1:20:070709:dimitrik.fr@gmail.com::EbBEv6i5fYwdlkUL:0000000000000000 0000000000000000000000004PB1 X-Hashcash: 1:20:070709:pgsql-performance@postgresql.org::k5TWfU9RUG2R4NgF:00000 00000000000000000000000026TK X-Virus-Scanned: Maia Mailguard 1.0.1 X-Archive-Number: 200707/68 X-Sequence-Number: 25752 --EgVrEAR5UttbsTXg Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable 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=3DOFF but using file system mounted in Direct > >I/O mode (means every write() system call called by PG really writes > >to disk before return)... >=20 > You'd have to turn that mode on on the data drives as well to get=20 > consistency, because fsync=3Doff disables checkpoint fsyncs of the data= =20 > files as well. BTW, it might be worth trying the different wal_sync_methods. IIRC, Jonah's seen some good results from open_datasync. --=20 Jim Nasby decibel@decibel.org EnterpriseDB http://enterprisedb.com 512.569.9461 (cell) --EgVrEAR5UttbsTXg Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.3 (FreeBSD) iD8DBQFGkptUdO30qud8SkgRAl8iAJ4s3IkZqGNqVq7DoHQcagnCyQkVBgCfcCin ldjN/xHattQVcsicvO71x/s= =rOSK -----END PGP SIGNATURE----- --EgVrEAR5UttbsTXg--