Received: from maia.hub.org (maia-3.hub.org [200.46.204.243]) by mail.postgresql.org (Postfix) with ESMTP id 056441337B93 for ; Mon, 7 Mar 2011 09:30:43 -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 46531-01 for ; Mon, 7 Mar 2011 13:30:35 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from cdptpa-omtalb.mail.rr.com (cdptpa-omtalb.mail.rr.com [75.180.132.122]) by mail.postgresql.org (Postfix) with ESMTP id 7EF6A133798E for ; Mon, 7 Mar 2011 09:30:35 -0400 (AST) X-Authority-Analysis: v=1.1 cv=pepdxKapwHuwCZNFD5uob2wvham6E+RljB0uXw08FdQ= c=1 sm=0 a=gDkBpS8wh10A:10 a=IkcTkHD0fZMA:10 a=qCTYjJJ2g1SgQhsHZAUATw==:17 a=jqzJR_k_GnpwPyuCc_kA:9 a=P2ABPhXwmLttiiKqqPkA:7 a=t_YQWTCmhpZzj0gN_eZQdNNLy14A:4 a=QEXdDO2ut3YA:10 a=qCTYjJJ2g1SgQhsHZAUATw==:117 X-Cloudmark-Score: 0 X-Originating-IP: 98.27.48.207 Received: from [98.27.48.207] ([98.27.48.207:54553] helo=[192.168.10.104]) by cdptpa-oedge03.mail.rr.com (envelope-from ) (ecelerity 2.2.3.46 r()) with ESMTP id 89/E2-19545-BFDD47D4; Mon, 07 Mar 2011 13:30:35 +0000 Message-ID: <4D74DDFA.70800@dunslane.net> Date: Mon, 07 Mar 2011 08:30:34 -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: 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> In-Reply-To: <4D74896C.5030402@enterprisedb.com> Content-Type: text/plain; charset=UTF-8; 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: 201103/463 X-Sequence-Number: 183713 On 03/07/2011 02:29 AM, Heikki Linnakangas wrote: > On 07.03.2011 01:28, Simon Riggs wrote: >> On Sun, 2011-03-06 at 18:09 -0500, Andrew Dunstan wrote: >>> >>> On 03/06/2011 05:51 PM, Simon Riggs wrote: >>>> Efficient transaction-controlled synchronous replication. >>> >>> I'm glad this is in, but I thought we agreed NOT to call it >>> "synchronous >>> replication". >> >> The discussion on the thread was that its not sync rep unless we have >> the strictest guarantees. We have the strictest guarantees, so it >> qualifies as sync rep. > > What do you mean by "strictes guarantees"? > > I don't see allow_synchronous_standby setting in the committed patch. > I presume you didn't make allow_synchronous_standby=off the default > behavior. Also, the documentation that describes this as two-safe > replication and claims that "the only possibility that data can be > lost is if both the primary and the standby suffer crashes at the same > time" needs big fat caveats to clarify that this doesn't actually > achieve those guarantees. > > Please change the name. > Previously, Simon said: > Truly "synchronous" requires two-phase commit, which this never was. So I too am confused about how it's now become "truly synchronous". Are we saying this give the same or better guarantees than a 2PC setup? cheers andrew