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Re: [PATCHES] Full page writes improvement, code update

From: "Simon Riggs" <simon(at)2ndquadrant(dot)com>
To: "Richard Huxton" <dev(at)archonet(dot)com>
Cc: "Zeugswetter Andreas ADI SD" <ZeugswetterA(at)spardat(dot)at>,"Koichi Suzuki" <suzuki(dot)koichi(at)oss(dot)ntt(dot)co(dot)jp>,<josh(at)agliodbs(dot)com>,<pgsql-hackers(at)postgresql(dot)org>,<pgsql-patches(at)postgresql(dot)org>
Subject: Re: [PATCHES] Full page writes improvement, code update
Date: 2007-03-30 11:21:29
Message-ID: 1175253689.4386.749.camel@silverbirch.site (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-patches
On Fri, 2007-03-30 at 11:27 +0100, Richard Huxton wrote:

> Is that always true? Could the backup not pick up a partially-written 
> page? Assuming it's being written to as the backup is in progress. (We 
> are talking about when disk blocks are smaller than PG blocks here, so 
> can't guarantee an atomic write for a PG block?)

Any page written during a backup has a backup block that would not be
removable by Koichi's tool, so yes, you'd still be safe.

i.e. between pg_start_backup() and pg_stop_backup() we always use full
page writes, even if you are running in full_page_writes=off mode.

-- 
  Simon Riggs             
  EnterpriseDB   http://www.enterprisedb.com



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