Received: from localhost (maia-1.hub.org [200.46.204.191]) by postgresql.org (Postfix) with ESMTP id 762C29FC3DF for ; Fri, 22 Jun 2007 14:12:11 -0300 (ADT) Received: from postgresql.org ([200.46.204.71]) by localhost (mx1.hub.org [200.46.204.191]) (amavisd-maia, port 10024) with ESMTP id 91664-08 for ; Fri, 22 Jun 2007 14:12:08 -0300 (ADT) 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 51CA19FB5FC for ; Fri, 22 Jun 2007 14:12:08 -0300 (ADT) Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) by sss.pgh.pa.us (8.14.1/8.14.1) with ESMTP id l5MHC25K023876; Fri, 22 Jun 2007 13:12:03 -0400 (EDT) To: Dan Gorman cc: "Simon Riggs" , "Toru SHIMOGAKI" , pgsql-performance@postgresql.org Subject: Re: PITR Backups In-reply-to: <31812EEE-22E7-41CD-B70F-CE861681BABC@hi5.com> References: <7E0807EE-B970-4869-A248-B838E42AD9EE@hi5.com> <9761.1182472005@sss.pgh.pa.us> <467B3459.9030808@oss.ntt.co.jp> <1182509748.9276.178.camel@silverbirch.site> <31812EEE-22E7-41CD-B70F-CE861681BABC@hi5.com> Comments: In-reply-to Dan Gorman message dated "Fri, 22 Jun 2007 04:10:36 -0700" Date: Fri, 22 Jun 2007 13:12:02 -0400 Message-ID: <23875.1182532322@sss.pgh.pa.us> From: Tom Lane X-Virus-Scanned: Maia Mailguard 1.0.1 X-Archive-Number: 200706/543 X-Sequence-Number: 25576 Dan Gorman writes: > This snapshot is done at the LUN (filer) level, postgres is un-aware > we're creating a backup, so I'm not sure how pg_start_backup() plays > into this ... That method works too, as long as you snapshot both the data files and WAL files --- when you start PG from the backup, it will think it crashed and recover by replaying WAL. So, assuming that the snapshot technology really works, it should be exactly as reliable as crash recovery is. If you saw a problem I'd be inclined to question whether there is some upstream component (OS or disk controller) that's reordering writes. regards, tom lane