In the last exciting episode, markir@paradise.net.nz (Mark Kirkwood) wrote:
> Mark Woodward wrote:
>> I'm not sure that I agree. At least in my experience, I wouldn't
>> have more than one installation of PostgreSQL in a production
>> machine. It is potentially problematic.
>
> I agree with you for production environments, but for development,
> test, support (and pre-sales) machines there are reasonable
> requirements for several.
I still have to ask what *specifically* you imagine to be the
"potentially problematic" aspect of having multiple installations on a
production system.
Furthermore, I have to vigorously disagree with the claim, as I have a
counterexample that has no "potentially" about it.
Up until version 8.0, when cache management changed dramatically,
there were kinds of workload that more or less *mandated* having
multiple installations. (... So that sequences of heavy updates
involving Pretty Large Rows wouldn't destroy the shared memory
cache...)
As far as I'm concerned, on versions 7.2 thru 7.4 (and we still have
7.4 systems in production), having LESS than two installations of
PostgreSQL on production machines is *specifically* and
*conspicuously* problematic for patterns of fairly heavy updates *that
we see*. We saw some very specific performance degradations on our
systems that were only alleviated by adding an extra install.
I've got performance statistics around to back this up, not that I
necessarily have permission to give them out ;-).
On those systems, NOT having multiple PG installs is *specifically*
problematic. Nothing "potential" about it; without the extra
instances around, performance was BAD.
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