Re: Page Checksums

On 12/18/11 5:55 PM, Greg Stark wrote:
> There is another way to look at this problem. Perhaps it's worth
> having a checksum *even if* there are ways for the checksum to be
> spuriously wrong. Obviously having an invalid checksum can't be a
> fatal error then but it might still be useful information. Rright now
> people don't really know if their system can experience torn pages or
> not and having some way of detecting them could be useful. And if you
> have other unexplained symptoms then having checksum errors might be
> enough evidence that the investigation should start with the hardware
> and get the sysadmin looking at hardware logs and running memtest
> sooner.

Frankly, if I had torn pages, even if it was just hint bits missing, I
would want that to be logged.  That's expected if you crash, but if you
start seeing bad CRC warnings when you haven't had a crash?  That means
you have a HW problem.

As long as the CRC checks are by default warnings, then I don't see a
problem with this; it's certainly better than what we have now.

-- 
Josh Berkus
PostgreSQL Experts Inc.
http://pgexperts.com