On Sun, 2011-01-02 at 11:11 -0600, Kevin Grittner wrote:
> Simon Riggs wrote:
>
> > Do you agree that requiring response from 2 sync standbys, or
> > locking up, gives us 94% server availability, but 99.9992% data
> > durability?
>
> I'm not sure how to answer that. The calculations so far have been
> based around up-time and the probabilities that you have a machine up
> at any moment and whether you can have confidence that if you do, you
> have all committed transactions represented. There's been an implied
> assumption that the down time is unplanned, but not much else. The
> above question seems to me to get into too many implied assumptions
> to feel safe throwing out a number without pinning those down a whole
> lot better. If, for example, that 2% downtime always means the
> machine irretrievably went up in smoke, hitting unavailable means
> things are unrecoverable. That's probably not the best assumption
> (at least outside of a combat zone), but what is?
Not really relevant. There's no room at all for downtime of any kind in
a situation where all servers must be available.
-- Simon Riggs http://www.2ndQuadrant.com/books/PostgreSQL Development, 24x7 Support, Training and Services
