Re: [HACKERS] [PATCHES] wal_checksum = on (default) | off

From: "Simon Riggs" <simon(at)2ndquadrant(dot)com>
To: "Gregory Stark" <stark(at)enterprisedb(dot)com>
Cc: "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>, "Bruce Momjian" <bruce(at)momjian(dot)us>, "Jim Nasby" <decibel(at)decibel(dot)org>, "Zeugswetter Andreas ADI SD" <ZeugswetterA(at)spardat(dot)at>, <pgsql-hackers(at)postgresql(dot)org>, <pgsql-patches(at)postgresql(dot)org>
Subject: Re: [HACKERS] [PATCHES] wal_checksum = on (default) | off
Date: 2007-01-11 23:10:38
Message-ID: 1168557038.3990.45.camel@silverbirch.site
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On Thu, 2007-01-11 at 17:06 +0000, Gregory Stark wrote:
> Having a CRC in WAL but not in the heap seems kind of pointless.

Yes...

> If your
> hardware is unreliable the corruption could anywhere.

Agreed.

Other DBMS have one setting for the whole server; I've never seen
separate settings for WAL and data.

> Depending on it to solve
> multiple problems means we can't offer the option to disable it
> because it
> would affect other things as well.
>
> What I would like to see is a CRC option that would put CRC checks in
> every
> disk page whether heap, index, WAL, control file, etc. I think we
> would
> default that to off to match our current setup most closely.
>
> Separately we would have a feature in WAL to detect torn pages so that
> we can
> reliably detect the end of valid WAL. That would have to always be on.
> But
> having it as a separate feature means the CRC could be optional.

Your thoughts seem logical to me.

It does seem a bigger project than I'd envisaged, but doable, one day.

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

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