Re: How much do the hint bits help?

On Wed, 2010-12-22 at 17:42 +0200, Heikki Linnakangas wrote:
> On 22.12.2010 17:31, Simon Riggs wrote:
> > On Wed, 2010-12-22 at 17:01 +0200, Heikki Linnakangas wrote:
> >> There's plenty of stuff in memory that's not covered by an
> >> application-level CRC. That's what ECC RAM is for.
> >
> > http://www.google.com/research/pubs/archive/35162.pdf
> >
> > Google research shows that each DIMM has an 8% chance per annum of
> > uncorrectable memory errors, even on ECC.
> 
> You misread that paper. From summary:

I read the paper in detail before I posted. If you think that finding an
error in my quote disproves anything, you should read the whole paper. I
see this:

Conclusion 1
"... Nonetheless, the remaining incidence of 0.22% per DIMM
per year makes a crash-tolerant application layer indispens-
able for large-scale server farms."

What you are arguing for is a protection system that will reduce in
effectiveness as we add more cache.

What I am arguing in favour of is an option to allow people to protect
their data, whatever the size of their cache. I'm not forcing you or
anyone to use it, but I think its an important option to be offering to
our users. 

-- Simon Riggs           http://www.2ndQuadrant.com/books/PostgreSQL Development, 24x7 Support, Training and Services