Received: from localhost (maia-2.hub.org [200.46.204.187]) by postgresql.org (Postfix) with ESMTP id CA7799FB4EC for ; Wed, 9 May 2007 14:49:34 -0300 (ADT) Received: from postgresql.org ([200.46.204.71]) by localhost (mx1.hub.org [200.46.204.187]) (amavisd-maia, port 10024) with ESMTP id 60042-06 for ; Wed, 9 May 2007 14:49:29 -0300 (ADT) X-Greylist: delayed 01:21:58.189451 by SQLgrey-1.7.4 Received: from brmea-mail-2.sun.com (brmea-mail-2.Sun.COM [192.18.98.43]) by postgresql.org (Postfix) with ESMTP id B31F79FB4C5 for ; Wed, 9 May 2007 14:49:30 -0300 (ADT) Received: from fe-amer-09.sun.com ([192.18.108.183]) by brmea-mail-2.sun.com (8.13.6+Sun/8.12.9) with ESMTP id l49HnTA9017338 for ; Wed, 9 May 2007 17:49:29 GMT Received: from conversion-daemon.mail-amer.sun.com by mail-amer.sun.com (Sun Java System Messaging Server 6.2-6.01 (built Apr 3 2006)) id <0JHS00801ALHR300@mail-amer.sun.com> (original mail from J.K.Shah@Sun.COM) for pgsql-performance@postgresql.org; Wed, 09 May 2007 11:49:29 -0600 (MDT) Received: from [10.63.106.155] ([194.42.125.16]) by mail-amer.sun.com (Sun Java System Messaging Server 6.2-6.01 (built Apr 3 2006)) with ESMTPSA id <0JHS00MY8C5X2410@mail-amer.sun.com>; Wed, 09 May 2007 11:49:11 -0600 (MDT) Date: Wed, 09 May 2007 18:49:16 +0100 From: Jignesh Shah Subject: Re: ZFS and Postgresql - WASRe: Best OS for Postgres 8.2 In-reply-to: <20070509170145.GS4504@alvh.no-ip.org> To: Alvaro Herrera Cc: =?windows-1252?Q?=3F=3F_Ian_Li?= , PostgreSQL Performance Message-id: <4642099C.3060504@sun.com> MIME-version: 1.0 Content-type: text/plain; format=flowed; charset=windows-1252 Content-transfer-encoding: 8BIT References: <1178574927.533849.90730@e51g2000hsg.googlegroups.com> <463FFF76.5070108@gmail.com> <4641F672.6090508@sun.com> <20070509170145.GS4504@alvh.no-ip.org> User-Agent: Thunderbird 2.0.0.0 (Windows/20070326) X-Virus-Scanned: Maia Mailguard 1.0.1 X-Archive-Number: 200705/205 X-Sequence-Number: 24595 But we still pay the penalty on WAL while writing them in the first place I guess .. Is there an option to disable it.. I can test how much is the impact I guess couple of %s but good to verify :-) ) Regards, Jignesh Alvaro Herrera wrote: > Jignesh Shah escribió: > > >> Now comes the thing that I am still exploring >> * Do we do checksum in WAL ? I guess we do .. Which means that we are >> now doing double checksumming on the data. One in ZFS and one in >> postgresql. ZFS does allow checksumming to be turned off (but on new >> blocks allocated). But of course the philosophy is where should it be >> done (ZFS or PostgreSQL). >> > > Checksums on WAL are not optional in Postgres, because AFAIR they are > used to determine when it should stop recovering. > >