Intel's new Nehalem-EX CPU for SMP servers brings eight cores, massive memory support, mainframe-like RAS features, and huge performance gains to large-scale workloads
While everyone has had a reasonably good time bashing the Itanium for the past several years, Itanium does have some significant upper-echelon features that x86/x64 systems could only dream about. Many of those features are in the RAS (Reliability, Availability, and Serviceability) arena -- capabilities like failed DIMM isolation, hot-swappable RAM, inter-socket memory mirroring, corrupt data containment, and CPU hot-adds. Until the release of the Nehalem-EX, these features simply didn't exist in the Xeon world. They do now.
The Nehalem-EX chip is designed for high-capacity SMP servers, scaling from two to 256 sockets at up to 256GB of addressable RAM per socket. Each chip has eight physical cores and 24MB of L3 cache, and can present 16 logical cores through Hyper-Threading. These are big-time numbers. It's possible to drop 1TB of RAM into a four-socket Nehalem-EX server.
[ Fast AES encryption, better scalability, and consistent per-core performance make the new six-core Xeon a worthy successor to Nehalem-EP. See "InfoWorld review: Intel's Westmere struts its stuff." ]
It's also important to understand the differences between the Nehalem-EX and the Westmere-EP. The Westmere-EP is built on a 32nm process, while the Nehalem-EX is built on a 45nm process. Where the Westmere-EP has six cores, like the X7400 Dunnington, the Nehalem-EX has eight. Where the Westmere-EP tops out at 12MB of L3 cache, the Nehalem-EX runs up to 24MB. Where the Westmere-EP runs up to 3.33GHz per core, the Nehalem-EX runs at 2.26GHz per core (at the moment). Where the Westmere-EP has two QuickPath interconnects, the Nehalem-EX has four, and can address twice the RAM of the Westmere-EP. Both offer Hyper-Threading, Intel VT virtualization hooks, and Turbo Mode.
The Nehalem-EX is suited for very large scaled workloads. Although the Westmere-EP has the bump in clock rate, it doesn't scale anywhere near the levels provided by the Nehalem-EX. That said, some workloads are better suited to the Westmere-EP, especially single-threaded tasks that benefit from the higher clock rate.
To test the Nehalem-EX, I opted for my suite of real-world concurrency tests. Lacking an Intel X7400-series server in the lab, I pitted a Dell R810 running two Intel X7560 Nehalem-EX CPUs against an older HP DL580 G3 running four Intel X7350 Tigerton CPUs. Note the differences between these systems before digging into the results: The HP DL580 had four quad-core X7350 CPUs running at 2.93GHz per core with a 4MB L3 cache. The Dell R810 had only two eight-core X7560s running at 2.26GHz per core with a 12MB cache. Whereas the X7560 Nehalem-EX CPUs support Hyper-Threading, the X7350s in the DL580 do not. It's not apples-to-apples, but it gives a good sense of what performance gains to expect if your servers are more than a year old and running on the X7300-series platform.
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