Six-core CPUs could have benefits for virtualisation

By Mark Fontecchio
Wednesday, 22 July, 2009

When it comes to upgrading to new six-core x86 processors, there's no substitute for real-world, in-house apps testing, IT pros say.

It's been more than a month since Advanced Micro Devices Inc. (AMD) announced its six-core Opteron x86 processor, code-named "Istanbul," and end users will eventually need to cease the pondering and start the testing of their own applications rather than relying on outside benchmarks.

"Third-party benchmarks are always a compromise with the way they're going to tell you how your system will be deployed," said Nathan Brookwood, an analyst and CPU expert at Insight64. "If you're going to make a substantial outlay, you would be crazy not to put your own software with whatever system you're going to use."

If users don't see a performance boost on their applications, it could mean the software needs tuning, "but that's a whole other issue," Brookwood said.

Opteron processor in action

For Steve Davidek, operations and systems administrator for the city of Sparks, application performance is of utmost importance. Many of the AMD-based servers -- quad-core Opteron HP ProLiants -- operate the police department's dispatch and records system. If Davidek and Sparks decided on a server refresh, they would most likely stick with AMD processors; in the past the application has run well on them. Though for some time, AMD rival Intel Corp. has offered a six-core Xeon processor.

"The vendor for the application had written the application using the AMDs and had good experience with them," he said. "And they were a little cheaper [than Intel servers], too, and that's often how it works in government."

Earlier this year, at the HP Technology Forum in Las Vegas, Davidek observed the six-core Opterons in action and was impressed. He is now working to secure budget funding -- either through city coffers or a grant -- so he can buy them.

Matthew Leeds, the vice president of IT operations at Gracenote, will test his company 's applications. The data center now runs dual-socket servers with quad-core Opteron processors and, depending on the application, 8 GB to 64 GB of memory.

"We don't benchmark in the way of running some third-party benchmarking application," he said. "We put our application on the box and run it and see how it behaves, and that's our benchmark. It's interesting to look at third-party benchmarks but they're not relevant. What matters to us is how our set of applications behaves."

Leeds added that after optimising their applications as much as possible, the question often comes down to how much memory they can dedicate to a CPU.

Opteron memory enhancements to boost performance

The new six-core Opteron has an L3 cache about three times as large as the AMD's first quad-core server chip, which is code-named "Barcelona" and was released in 2007. Compared with the most recent quad-core Opterons, however, the memory specs look the same.

"If it's Barcelona, they would see some significant enhancements in performance and definite improvements in performance per watt," Brookwood said.

Memory is an important consideration for Leeds. Gracenote is in the media management business, so if someone runs a music application recognised by Gracenote and inserts a CD, the company's application will find all the CD's information. The result is tens of millions of queries a day, with an average query time of just a few milliseconds.

As a result, Gracenote runs many in-core memory databases to make accessing the information quicker. So memory is a big deal.

Ditto for Davidek and the Sparks police department. Since the AMD-based servers run the police dispatch system, quick response times can have a real effect on how quickly police respond to 911 calls.

"The police system can be very memory-intensive," he said. "AMD was a better fit for what we were doing at the time."

Virtualised workloads could see benefits

Brookwood said that if applications are optimised for multithreading, more cores will help. In addition, as companies virtualize their workloads, consolidating from a one-app, one-server topology to many virtualized servers on larger machines, more processor cores can help.

"The Istanbul processor is a natural for those applications," Brookwood said. "If the customer is already using AMD infrastructure and installed a bunch of servers back in 2006 when AMD was selling dual-core Opterons, they may discover that upgrading from dual-core to Istanbul gives them a huge bang for the buck."

Considering Nehalem instead

Many users will consider replacing their AMD gear with Intel Xeon-based servers. Leeds is concerned about the newest Xeon, which is code-named "Nehalem" and uses DDR3 memory, which is a more expensive memory part than the DDR2 that Opteron uses. Still, Gracenote plans to test Xeon as well.

A benefit to the six-core Opteron is that it can fit in the same socket as the dual cores sold in 2006. So all it takes is a CPU swap rather than replacing the entire server, which is what AMD shops would have to do if they switch to Xeon-based servers.

Brookwood recommends that if IT pros do the CPU swap themselves, they upgrade firmware before swapping out the processors. Otherwise, the server might not restart.

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