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October 29, 2007


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Open Systems Guy

What's the problem? Random, non sequential reads are what most transactional and database workloads do most of the time, and the performance these application will get is pretty much directly proportional to the spindle count. Cache can only really help you write or do predictable reads (less than 30%, in my experience)

While I don't agree that the SPC is a silver bullet for comparing disk systems, and I certainly don't think it even remotely mimics the real life environment of any company's server room, I do think these results are right in line with what I would expect from a good benchmark. More spindles should yield higher "behind cache" performance. The benefit of benchmarking is that it allows buyers who care about performance to find out if this is true for the system they're thinking of acquiring- I'll bet that on an old disk system, the performance measured would quickly plateau off as drives continued to be added. I would also expect this of low power controllers that have more intensive features (like the write anywhere file system in a Netapps box).

Of course, performance is a distant third in my book behind features and reliability, and every corporate IT person is going to have to prioritize their needs.


No issue with what you said, Open Systems Guy. The results are not at all unexpected for a benchmark like SPC-1 - like I stated in the beginning of my post. As I said, the result is not astounding, and neither is this rocket science.

But given the complete predictability of the results, why bother having a benchmark? What is a vendor trying to prove or disprove by publishing a result that uses much more raw storage than the adressable storage? Why should one cook the books in this fashion?

Maybe lower end systems will reveal choke points before disk IO saturates, but for all the systems benchmarked to date, the spindle count is it.

I agree that functionality and availability should come before, especially for high end arrays.

Open Systems Guy

In my experience, even some mid range systems level off before disk IO saturation. This may not be an issue- if I use a Netapps filer, chances are I am paying for its unique snapshot algorithm, but if I didn't know that it could choke on IO if I hit a certain level of performance, then I might be unpleasantly surprised.

All I'm saying is that some sort of benchmarking should be made available. Just because most systems will perform the same per spindle does not negate the need for a benchmark to support vendor data.

Barry Whyte

Some additional analysis over on my blog - would have posted here, but needed to include the complete pictures :)


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