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Re: Block-level CRC checks

From: Florian Weimer <fweimer(at)bfk(dot)de>
To: Gregory Stark <stark(at)enterprisedb(dot)com>
Cc: Paul Schlie <schlie(at)comcast(dot)net>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Brian Hurt <bhurt(at)janestcapital(dot)com>, <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Block-level CRC checks
Date: 2008-10-02 07:41:47
Message-ID: 823ajf4f5w.fsf@mid.bfk.de (view raw or flat)
Thread:
Lists: pgsql-hackers
* Gregory Stark:

> I've also seen single-bit errors caused by bad memory in a network interface.
> *Twice*. Particularly nasty since the CRC on TCP/IP packets is only 16-bit so
> a large enough ftp transfer would eventually finish despite the packet loss
> but with the occasional bits flipped. In these days of SAN/NAS and SCSI over
> IP that's pretty scary...

I've seen double-bit errors in Internet routing which canceled each
other out (the Internet checksum is just a sum, not a CRC, so this
happens with some probability once you've got bit errors with a
multiple-of-16 periodicity).

-- 
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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