Received: from maia.hub.org (maia-2.hub.org [200.46.204.251]) by mail.postgresql.org (Postfix) with ESMTP id D83D91337B3E for ; Tue, 16 Nov 2010 19:31:53 -0400 (AST) 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 18262-05 for ; Tue, 16 Nov 2010 23:31:47 +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 8D9B91337B34 for ; Tue, 16 Nov 2010 19:31:46 -0400 (AST) 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 oAGNVYLi009059; Tue, 16 Nov 2010 18:31:34 -0500 (EST) To: Josh Berkus cc: pgsql-performance@postgresql.org, Greg Smith Subject: Re: Defaulting wal_sync_method to fdatasync on Linux for 9.1? In-reply-to: <4CE312D9.6030503@agliodbs.com> References: <4CCDCAA3.4050805@2ndquadrant.com> <201011010010.28724.andres@anarazel.de> <4CD472CC.80006@2ndquadrant.com> <4CE2EBF8.4040602@2ndquadrant.com> <4CE312D9.6030503@agliodbs.com> Comments: In-reply-to Josh Berkus message dated "Tue, 16 Nov 2010 15:25:13 -0800" Date: Tue, 16 Nov 2010 18:31:34 -0500 Message-ID: <9058.1289950294@sss.pgh.pa.us> From: Tom Lane X-Virus-Scanned: Maia Mailguard 1.0.1 X-Spam-Status: No, hits=-1.91 tagged_above=-10 required=5 tests=BAYES_00=-1.9, T_RP_MATCHES_RCVD=-0.01 X-Spam-Level: X-Archive-Number: 201011/270 X-Sequence-Number: 41294 Josh Berkus writes: > On 11/16/10 12:39 PM, Greg Smith wrote: >> I want to next go through and replicate some of the actual database >> level tests before giving a full opinion on whether this data proves >> it's worth changing the wal_sync_method detection. So far I'm torn >> between whether that's the right approach, or if we should just increase >> the default value for wal_buffers to something more reasonable. > We'd love to, but wal_buffers uses sysV shmem. Well, we're not going to increase the default to gigabytes, but we could very probably increase it by a factor of 10 or so without anyone squawking. It's been awhile since I heard of anyone trying to run PG in 4MB shmmax. How much would a change of that size help? regards, tom lane