Initially, the introduction of more cores to the mix is good for virtualization allowing us to scale more gracefully and confidently as compared to hyper-threading. While hyper-threading is reported to increase scheduling efficiency in vSphere, it is not effectively a core. Until Nehalem-EX is widely available and we can evaluate 4P performance of hyper-threading in loaded virtual environments I'm comfortable awarding hyper-threading a 5% performance bonus - all things being equal.
[caption id="attachment_435" align="alignright" width="300" caption="AMD's Value Shift"]
[/caption]What's Coming?
That said, where is AMD going with Opteron in the near future and how will that affect Opteron-based eco-systems? At least one thing is clear: compatibility is assured and performance - at the same thermal footprint - will go up. So let's look at the ramifications of the new models/sockets and compare them to our well-known 2000/8000 series to glimpse the future.
A fundamental shift away from DDR2 and towards DDR3 for the new sockets is a major difference. Like the Phenom II, Core i7 and Nehalem processors, the new Opteron will be a DDR3 specimen. Assuming DDR3 pricing continues to trend down and the promise of increased memory bandwidth is realized in the HT3/DCA2 and Opteron, DDR3 will deliver solid performance in 4000 and 6000 configurations.
Opteron 6000: Socket G34
From the announcement, G34 is analogous to the familiar 8000-series line with one glaring exception: no 8P on the road-map. In the 2010-2011 time frame, we'll see 8-core, 12-core and 16-core variants with a new platform being introduced in 2012. Meanwhile, the 6000-series will support 4-channels of "unbuffered" or "registered" DDR3 across up to 12DIMMs per socket (3 banks by 4 channels). Assuming 6000 will support DDR3-1600, the theoretical bandwidth of a 4 channel design would yield memory bandwidths in the 40-50GB/sec range per link (about twice Istanbul's).
[caption id="attachment_433" align="alignright" width="300" caption="AMD 2010-2013 Road-map"]
[/caption]With a maximum module density of 16GB, a 12-DIMM by 4-socket system could theoretically contain 768GB of DDR3 memory. In 2011, that equates to 12GB/core in a 4-way, 64-core server. At 4:1 consolidation ratios for typical workloads, that's 256 VM/host at 3GB/VM (4GB/VM with page sharing) and an average of 780MB/sec of memory bandwidth per VM. I think the math holds-up pretty well against today's computing norms and trends.
