Received: from maia.hub.org (maia-3.hub.org [200.46.204.243]) by mail.postgresql.org (Postfix) with ESMTP id 4A9E71337B4E for ; Mon, 7 Mar 2011 11:51:58 -0400 (AST) Received: from mail.postgresql.org ([200.46.204.86]) by maia.hub.org (mx1.hub.org [200.46.204.243]) (amavisd-maia, port 10024) with ESMTP id 18012-03 for ; Mon, 7 Mar 2011 15:51:51 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from cdptpa-omtalb.mail.rr.com (cdptpa-omtalb.mail.rr.com [75.180.132.121]) by mail.postgresql.org (Postfix) with ESMTP id D1541133798E for ; Mon, 7 Mar 2011 11:51:50 -0400 (AST) X-Authority-Analysis: v=1.1 cv=pepdxKapwHuwCZNFD5uob2wvham6E+RljB0uXw08FdQ= c=1 sm=0 a=gDkBpS8wh10A:10 a=8nJEP1OIZ-IA:10 a=qCTYjJJ2g1SgQhsHZAUATw==:17 a=8pif782wAAAA:8 a=UGmWaC7xP1CCUhx6IlIA:9 a=q4NE7hqY7_I8IakfGAAA:7 a=Kw0WAqZwqe_-7-Heu38NMAlW1pwA:4 a=wPNLvfGTeEIA:10 a=qCTYjJJ2g1SgQhsHZAUATw==:117 X-Cloudmark-Score: 0 X-Originating-IP: 98.27.48.207 Received: from [98.27.48.207] ([98.27.48.207:33272] helo=[192.168.10.104]) by cdptpa-oedge03.mail.rr.com (envelope-from ) (ecelerity 2.2.3.46 r()) with ESMTP id 76/EE-19545-61FF47D4; Mon, 07 Mar 2011 15:51:50 +0000 Message-ID: <4D74FF15.1070804@dunslane.net> Date: Mon, 07 Mar 2011 10:51:49 -0500 From: Andrew Dunstan User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.13) Gecko/20101209 Fedora/3.1.7-0.35.b3pre.fc13 Lightning/1.0b3pre Thunderbird/3.1.7 MIME-Version: 1.0 To: Heikki Linnakangas CC: Aidan Van Dyk , Simon Riggs , pgsql-hackers@postgresql.org Subject: Re: Re: [COMMITTERS] pgsql: Efficient transaction-controlled synchronous replication. References: <4D741441.2090704@dunslane.net> <1299454125.1696.6138.camel@ebony> <4D74896C.5030402@enterprisedb.com> <4D74DDFA.70800@dunslane.net> <4D74E584.7080409@enterprisedb.com> <4D74E9FA.7070202@dunslane.net> <4D74F3AE.9000802@dunslane.net> <4D74FDEC.5040406@enterprisedb.com> In-Reply-To: <4D74FDEC.5040406@enterprisedb.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: Maia Mailguard 1.0.1 X-Spam-Status: No, hits=2.419 tagged_above=-5 required=5 tests=BAYES_00=-1.9, FS_REPLICA=3.599, RCVD_IN_DNSWL_NONE=-0.0001, SARE_SPEC_REPLICA=0.72 X-Spam-Level: ** X-Archive-Number: 201103/473 X-Sequence-Number: 183723 On 03/07/2011 10:46 AM, Heikki Linnakangas wrote: > On 07.03.2011 17:03, Andrew Dunstan wrote: >> This is about expectations. The thing that worries me is that the use of >> this term might cause some people NOT to use 2PC because they think they >> are getting an equivalent guarantee, when in fact they are not. And >> that's hardly unreasonable. Here for example is what wikipedia says >> : >> >> Synchronous replication - guarantees "zero data loss" by the means >> of atomic write operation, i.e. write either completes on both sides >> or not at all. Write is not considered complete until >> acknowledgement by both local and remote storage. > > Hmm, I've read that wikipedia definition before, but the "atomic" part > never caught my eye. You do get zero data loss with what we have; if a > meteor strikes the master, no acknowledged transaction is lost. I find > that definition a bit confusing. Maybe it is - I agree the difference might be small. I'm just trying to make sure we don't use a term that could mislead reasonable people about what we're providing. If we're satisfied that we aren't, then keep it. cheers andrew