From: | "J(dot) Andrew Rogers" <jrogers(at)neopolitan(dot)com> |
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To: | "Jonah H(dot) Harris" <jonah(dot)harris(at)gmail(dot)com> |
Cc: | pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: COMMIT NOWAIT Performance Option |
Date: | 2007-03-01 02:22:58 |
Message-ID: | 98A04B82-95A4-44C7-BED3-64F5F1DB2E6E@neopolitan.com |
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Lists: | pgsql-hackers |
On Feb 28, 2007, at 4:40 PM, Jonah H. Harris wrote:
> Oracle, Microsoft, IBM, Sybase, Teradata, MySQL, and Firebird have a
> clever feature called page checksumming which I think we should copy
> because it's simple and effective at detecting page-level corruption
> due to torn pages and/or faulty storage hardware.
Any system that does enough I/O will occasionally generate corrupted
pages in the complete absence of any other detectable fault or
hardware failure. A fair amount has been written about it with
respect to large-scale computing and it happens often enough when
systems start getting large that just about everyone implements
software I/O checksumming eventually to deal with the problem. I
simply assumed that PostgreSQL was doing the same since it is
definitely used for systems that are large enough that this becomes a
statistically significant issue.
A popular alternative to CRC32 for this purpose is the significantly
cheaper and almost as effective is the Adler32 algorithm. I know
Google used this algorithm when they added checksumming to their
database to tame inexplicable transient corruption.
Cheers,
J. Andrew Rogers
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