Received: from maia.hub.org (maia-2.hub.org [200.46.204.251]) by mail.postgresql.org (Postfix) with ESMTP id 4A70663383B for ; Fri, 7 May 2010 20:51:23 -0300 (ADT) Received: from mail.postgresql.org ([200.46.204.86]) by maia.hub.org (mx1.hub.org [200.46.204.251]) (amavisd-maia, port 10024) with ESMTP id 28669-09 for ; Fri, 7 May 2010 23:51:15 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from sss.pgh.pa.us (sss.pgh.pa.us [66.207.139.130]) by mail.postgresql.org (Postfix) with ESMTP id 583CB63248C for ; Fri, 7 May 2010 20:51:16 -0300 (ADT) Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) by sss.pgh.pa.us (8.14.2/8.14.2) with ESMTP id o47NnFYI003861; Fri, 7 May 2010 19:49:15 -0400 (EDT) To: Bernd Helmle cc: Kevin Grittner , Andrew Dunstan , pgsql-hackers@postgresql.org Subject: Re: no universally correct setting for fsync In-reply-to: References: <4BE3D3930200002500031382@gw.wicourts.gov> <4BE425F7.30804@dunslane.net> <4BE3E205020000250003138F@gw.wicourts.gov> Comments: In-reply-to Bernd Helmle message dated "Sat, 08 May 2010 01:32:59 +0200" Date: Fri, 07 May 2010 19:49:15 -0400 Message-ID: <3860.1273276155@sss.pgh.pa.us> From: Tom Lane X-Virus-Scanned: Maia Mailguard 1.0.1 X-Spam-Status: No, hits=-1.91 tagged_above=-5 required=5 tests=BAYES_00=-1.9, T_RP_MATCHES_RCVD=-0.01 X-Spam-Level: X-Archive-Number: 201005/382 X-Sequence-Number: 162045 Bernd Helmle writes: > I've recently even started to wonder if the performance gain with fsync=off > is still that large on modern hardware. While testing large migration > procedures to a new version some time ago (on an admitedly fast storage) i > forgot here and then to turn it off, without a significant degradation in > performance. That says to me either that you're using a battery-backed write cache, or your fsyncs don't really work (no write barriers or something like that). regards, tom lane