Обсуждение: AW: Re: TODO list

> > 1. Under "RELIABILITY/MISC", add:
> > 
> >   Write out a CRC with each data block, and verify it on reading.

> TODO updated.  I know we did number 2, but did we agree on #1 and is it
> done?

Has anybody done performance and reliability tests with CRC64 ? 
I think it must be a CPU eater. It looks a lot more complex than a CRC32.

Since we need to guard a maximum of 32k bytes for pg pages I would - if at all -
consider to use a 32bit adler instead of a CRC, since that is a lot cheaper
to calculate. 

Andreas

Zeugswetter Andreas SB  <ZeugswetterA@wien.spardat.at> writes:
> Has anybody done performance and reliability tests with CRC64 ? 
> I think it must be a CPU eater. It looks a lot more complex than a CRC32.

On my box (PA-RISC) the inner loop is about 14 cycles/byte, vs. about
7 cycles/byte for CRC32.  On almost any machine, either one will be
negligible in comparison to the cost of disk I/O.

> Since we need to guard a maximum of 32k bytes for pg pages I would -
> if at all - consider to use a 32bit adler instead of a CRC, since that
> is a lot cheaper to calculate.

You are several months too late to re-open that argument.  It's done and
it's not changing for 7.1.
        regards, tom lane