Received: from localhost (maia-5.hub.org [200.46.204.182]) by postgresql.org (Postfix) with ESMTP id 6C9539FB4A7; Wed, 11 Apr 2007 19:48:44 -0300 (ADT) Received: from postgresql.org ([200.46.204.71]) by localhost (mx1.hub.org [200.46.204.182]) (amavisd-maia, port 10024) with ESMTP id 93984-05; Wed, 11 Apr 2007 19:48:37 -0300 (ADT) X-Greylist: from auto-whitelisted by SQLgrey-1.7.4 X-Greylist: from auto-whitelisted by SQLgrey-1.7.4 Received: from sss.pgh.pa.us (sss.pgh.pa.us [66.207.139.130]) by postgresql.org (Postfix) with ESMTP id 1D12A9FB483; Wed, 11 Apr 2007 19:48:41 -0300 (ADT) Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) by sss.pgh.pa.us (8.13.6/8.13.6) with ESMTP id l3BMmNUR006051; Wed, 11 Apr 2007 18:48:23 -0400 (EDT) To: Koichi Suzuki cc: Simon Riggs , josh@agliodbs.com, pgsql-hackers@postgresql.org, pgsql-patches@postgresql.org Subject: Re: [HACKERS] Full page writes improvement, code update In-reply-to: <461C3557.6040201@oss.ntt.co.jp> References: <460886E8.6040907@oss.ntt.co.jp> <4609CAC3.7060008@oss.ntt.co.jp> <1175072848.4386.323.camel@silverbirch.site> <200703291145.28574.josh@agliodbs.com> <1175200117.4386.616.camel@silverbirch.site> <460C611E.6090800@oss.ntt.co.jp> <27693.1176226131@sss.pgh.pa.us> <461C3557.6040201@oss.ntt.co.jp> Comments: In-reply-to Koichi Suzuki message dated "Wed, 11 Apr 2007 10:09:43 +0900" Date: Wed, 11 Apr 2007 18:48:23 -0400 Message-ID: <6050.1176331703@sss.pgh.pa.us> From: Tom Lane X-Virus-Scanned: Maia Mailguard 1.0.1 X-Archive-Number: 200704/322 X-Sequence-Number: 1889 Koichi Suzuki writes: > For more information, when checkpoint interval is one hour, the amount > of the archived log size was as follows: > cp: 3.1GB > gzip: 1.5GB > pg_compresslog: 0.3GB The notion that 90% of the WAL could be backup blocks even at very long checkpoint intervals struck me as excessive, so I went looking for a reason, and I may have found one. There has been a bug in CVS HEAD since Feb 8 causing every btree page split record to include a backup block whether needed or not. If these numbers were taken with recent 8.3 code, please retest with current HEAD. regards, tom lane