Re: COMMIT NOWAIT Performance Option

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