Navigate the multicore minefield

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Navigate the multicore minefield

John Enck, vice-president and research director at Gartner

The advent of dual-core and quad-core processors in the x86 server market represents a major change in how performance is delivered to IT organisations. In the past, performance increases were delivered by increasing the execution rate - the frequency - of the processors, and thus any application would run faster on a faster processor.

This is not the case with multicore processors. For an application to enjoy increased performance, it must be a "well-threaded" application. A well-threaded application is written so that some of its tasks - ie. threads - can run concurrently on multiple processor cores. If an application is not well-threaded, then all the cores in the world will not give it more performance.

The software issue around multiple cores will present a big challenge, and there are good sources of guidance available online. But it is not just software that will be potentially affected by multicore x86 servers. The other item that has the potential to change is buying behaviour.

In recent years, dual-socket configurations have been the sweet spot in the x86 server market. In these configurations each socket was populated with a single core processor, so for many years dual-socket was synonymous with dual-processor. This dual-socket configuration represented about 70% of x86 server shipments and revenue in 2006.

Because of the volume of purchases, dual-socket configurations have had the best manufacturing economics and the best price competition in the x86 server market. As a result, most enterprises have standardized on dual-socket configurations for their standard x86 server purchase.

The introduction of multicore x86 processors has the potential to change the market dynamics. In 2007, a dual-socket configuration can contain single or multicore processors. This is equally true of single-socket and quad-socket configurations. For example, you can buy a single-socket server with a dual-core processor or a dual-socket server with two single-core processors. They are both dual-processor configurations, which adds complexity to buying decisions.

Server suppliers are not making these new decisions any easier either. Some suppliers are continuing to suggest that dual-socket configurations are the wisest buy, while others are suggesting users move up to quad-socket configurations to better support larger workloads driven by virtualisation. Some suppliers are even suggesting that you downsize to single-socket servers and increase the core count of the processors.

On this last point, it will, in some cases, be possible to use single-socket configurations in place of dual-socket configurations, but IT directors would be wise to exercise caution here.

Single-socket configurations often do not offer the same redundancy capabilities for fans and power supplies and often cannot be configured to handle the same amount of memory and input/output (I/O) as dual-socket servers. A single dual-core processor does not deliver the same performance as two single-core processors.

However, if you have been using single-socket configurations successfully, you can certainly continue using them.

For organisations that are operating fewer, larger servers, the higher costs for quad-socket configurations may be offset by operational efficiencies. But denser server workloads involve more complexity, and more complexity may lead to administrative inefficiencies.

Be careful that you are not paying more in hardware and operational costs.

The full Gartner report >>

Rebirth for the x86: what to buy >>

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This was first published in May 2007

 

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