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 greg@xxxxxxxxxxxxxxx www.2ndQuadrant.us -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
