>I've seen quite a few folks touting the Opteron as 2.5x
>faster with postgres than a Xeon box. What makes the
>Opteron so quick? Is it that Postgres really prefers to
>run in 64-bit mode?
I don't know about 2.5x faster (perhaps on specific types
of loads), but the reason Opterons rock for database
applications is their insanely good memory bandwidth and
latency that scales much better than the Xeon. Opterons
also have a ccNUMA-esque I/O fabric and two dedicated
on-die memory channels *per processor* -- no shared bus
there, closer to real UNIX server iron than a glorified
PC.
We run a large Postgres database on a dual Opteron in
32-bit mode that crushes Xeons running at higher clock
speeds. It has little to do with bitness or theoretical
instruction dispatch, and everything to do with the
superior memory controller and I/O fabric. Databases are
all about moving chunks of data around and the Opteron
systems were engineered to do this very well and in a very
scalable fashion. For the money, it is hard to argue with
the price/performance of Opteron based servers. We
started with one dual Opteron postgres server just over a
year ago (with an equivalent uptime) and have considered
nothing but Opterons for database servers since. Opterons
really are clearly superior to Xeons for this application.
I don't work for AMD, just a satisfied customer. :-)
re: 6 disks. Unless you are tight on disk space, a hot
spare might be nice as well depending on your needs.
Cheers,
J. Andrew Rogers