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

From: Florian Weimer <fw(at)deneb(dot)enyo(dot)de>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: "Simon Riggs" <simon(at)2ndquadrant(dot)com>,pgsql-hackers(at)postgresql(dot)org, pgsql-patches(at)postgresql(dot)org
Subject: Re: [HACKERS] wal_checksum = on (default) | off
Date: 2007-01-04 20:16:02
Message-ID: 87r6uawnst.fsf@mid.deneb.enyo.de (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-patches
* Tom Lane:

> Florian Weimer <fweimer(at)bfk(dot)de> writes:
>> Have you tried switching to Adler32 instead of CRC32?
>
> Is anything known about the error detection capabilities of Adler32?
> There's a lot of math behind CRCs but AFAIR Adler's method is pretty
> much ad-hoc.

Correct me if I'm wrong, but the main reason for the WAL CRC is to
detect partial WAL writes (due to improper caching, for instance).
This means that you're out of the realm of traditional CRC analysis
anyway, because the things you are guarding against are neither burts
errors nor n-bit errors (for small n).

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