Scott Carey wrote:
> But the select count(*) query, cached in RAM is 3x faster in one system than the other. The CPUs aren't 3x different performance wise. Something else may be wrong here.
> An individual Core2 Duo 2.93Ghz should be at most 50% faster than a 2.2Ghz Opteron for such a query. Unless there are some compile options that are set wrong. I would check the compile options.
Sure, it might be. But I've seen RAM on an Intel chip like the E7500
here (DDR3-1066 or better, around 10GB/s possible) run almost 3X as fast
as what you'll find paired with an Opteron 2427 (DDR2-800, closer to
3.5GB/s). Throw in the clock differences and there you go.
I've been wandering around for years warning that the older Opterons on
DDR2 running a single PostgreSQL process are dog slow compared to the
same thing on Intel. So that alone might actually be enough to account
for the difference. Ultimately the multi-processor stuff is what's more
important to most apps, though, which is why I was hinting to properly
run that instead.
Greg Smith 2ndQuadrant US Baltimore, MD
PostgreSQL Training, Services and Support
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