AnandTech has a good benchmarking article up that shows the amazing performance of the Nehalem-based Xeon 5570 vs. the latest AMD server chips and several older Xeon chip families. For the SQL Server 2005 based benchmarks, the Xeon 5570 is doing about twice as well as the Xeon 5450 (Penryn-based Harpertown). They did a pretty good job setting up the hardware in such a way (with multiple SSDs for data drives) to minimize disk bottlenecks, so they could measure the comparative CPU performance.
They also put some effort into measuring power consumption, which is a big issue in the server world.
Here is a quote from their conclusion:
“The Xeon X55xx series simply crushes the competition and reduces the older Xeons to expensive space heaters, with the exception of the rendering and dense matrix HPC market. If you are consolidating your servers, buying a new heavyweight back end database server or mail server, there is only one choice at this moment: the Xeon X55xx series. Period.”
Here are the two SQL Server 2005 specific graphs:
This confirms my opinion that two socket Xeon 5570 systems (which will be able to hold 72GB of RAM with 4GB sticks) will be excellent replacements for old four-socket Xeon 70xx and 71xx systems. There are huge savings in SQL Server license costs, power costs, and management costs.