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« i Can ... Remember Craig | Main | i Can … Excel at SAP Benchmarking With IBM i 6.1 and POWER7 »

February 08, 2010


If we talk about performance, CPW is not fair to new Power System equipments running Power6 or future systems running Power7.
CPW is a database performance spec, and considering we can attach external storage including SAN Volume Controller and lots of arrays, even SSDs, we can get more performance from a system depending on disk configuration.

Thanks for the great comment, and I apologize for taking so long to reply to it.

The team responsible for publishing CPW has the notion of fair comparisons foremost in their mind as they set up and run the workload CPW. It might be helpful to know that this team does not think of CPW as a benchmark; it is a workload intended solely for relative positioning of the processor and memory subsystem. Certainly the team works to ensure good performance results, ensuring that both the processor hardware and software used in its support are executing efficiently. And, yes, it is not unreasonable for the team to use advanced I/O subsystems and the possible use of SSDs is in the future. But when if we change the I/O subsystem, the same I/O subsystem will be used within to compare to preceding comparison systems as well. That is part of the reason that the notion of a CPW rating gets published as opposed to some notion of throughput (transactions/minute). If changes are made to the CPW workload or environment, adjustments are made to the definition of CPW in order to ensure appropriate and consistent bridging between systems. The CPW team knows how CPW results are being used and works hard to ensure its consistency. Our goal with CPW performance reporting is to allow customers and business partners running similar environments to experience performance roughly mirroring the CPW results.

It is fair, though, to question just how well the CPW workload proper represents your use of a system. It is just one database transaction processing workload after all. Every workload uses the entire system in different ways. But, again, CPW's purpose is to provided an informed judgement of the relative compute capacity of each system. As such, it attempts to aggressively use all aspects of the processor complex. Explaining what that means alone can take quite a while, but may we suggest - if extra detail is useful to you - that you find the paper "Of Gigahertz and CPWs" mentioned in my blog for an overview of the processor complex that the CPW workload is driving.

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