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Re: Block-level CRC checks

From: Florian Weimer <fweimer(at)bfk(dot)de>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: "Jonah H(dot) Harris" <jonah(dot)harris(at)gmail(dot)com>, pgsql(at)mohawksoft(dot)com, "Hannu Krosing" <hannu(at)2ndquadrant(dot)com>, Decibel! <decibel(at)decibel(dot)org>, "Alvaro Herrera" <alvherre(at)commandprompt(dot)com>, "Pg Hackers" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Block-level CRC checks
Date: 2008-10-01 16:12:05
Message-ID: 828wt88fca.fsf@mid.bfk.de (view raw or flat)
Thread:
Lists: pgsql-hackers
* Tom Lane:

> No, not at all.  Block-level checksums would be an order of magnitude
> more expensive: they're on bigger chunks of data and they'd be done more
> often.

For larger blocks, checksumming can be parallelized at the instruction
level, especially if the block size is statically known.  And for
large blocks, Adler32 isn't that bad compared to CRC32 from a error
detection POV, so maybe you could use that.

I've seen faults which were uncovered by page-level checksumming, so
I'd be willing to pay the performance cost. 8-/

-- 
Florian Weimer                <fweimer(at)bfk(dot)de>
BFK edv-consulting GmbH       http://www.bfk.de/
Kriegsstra├če 100              tel: +49-721-96201-1
D-76133 Karlsruhe             fax: +49-721-96201-99

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