Re: Is full_page_writes=off safe in conjunction with

From: Hannu Krosing <hannu(at)skype(dot)net>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: pgsql-hackers(at)postgreSQL(dot)org
Subject: Re: Is full_page_writes=off safe in conjunction with
Date: 2006-04-14 21:19:24
Message-ID: 1145049565.7917.1.camel@localhost.localdomain
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Ühel kenal päeval, R, 2006-04-14 kell 16:40, kirjutas Tom Lane:

> I think we had originally argued that there was no problem anyway
> because the kernel should cause the page write to appear atomic to other
> processes (since we issue it in a single write() command). But that's
> only true if the backup-taker reads in units that are multiples of
> BLCKSZ. If the backup-taker reads, say, 4K at a time then it's
> certainly possible that it gets a later version of the second half of a
> page than it got of the first half. I don't know about you, but I sure
> don't feel comfortable making assumptions at that level about the
> behavior of tar or cpio.
>
> I fear we still have to disable full_page_writes (force it ON) if
> XLogArchivingActive is on. Comments?

Why not just tell the backup-taker to take backups using 8K pages ?

---------------
Hannu

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