A proud 3PAR introduced their new T series at the beginning of September. If you're into drag racing, they showed a really nice set of numbers in their latest SPC-1 speed test.
3PAR quote quite a few of them in their press release, and in a breathless summary, declared that they had been achieved...
"...with 83% capacity utilization and without complex configuration or performance tuning"
Great utilization too! And here's the SPC-1 disclosure (the devil is in the detail, believe me, so I always check) that explains; Data Protection Level: Mirroring
OK, so it's not a complex configuration (EMC supports it too, so it really can't be that difficult), and although mirroring might be considered a performance tuning advantage -- hey, use RAID-5 if the box is that good! -- I'll let it pass.
Anyone see the problem here? 83% capacity utilisation? And with all the disks mirrored?
200% Surprised
How do you get 83% utilization when everything is mirrored? Heck, how do you get anywhere near 50%?
Eventually, I got the answer.
It's Bistromathics
The late Douglas Adams summarised his new found principle best.
"Bistromathics itself is simply a revolutionary new way of understanding the behaviour of numbers.
"Just as Albert Einstein's general relativity theory observed that space was not an absolute but depended on the observer's movement in time, and that time was not an absolute, but depended on the observer's movement in space, so it is now realized that numbers are not absolute, but depend on the observer's movement in restaurants."
Now we can add to the list. Bistromathics applies not just in restaurants, but 3PAR press releases too.
Bistro Manager Explains
So, 3PAR's newly hired Marc Farley came and helped out a puzzled NetApp diner. He was kind enough to explain the complexities of the 3PAR bill of fare.
- [Puzzled Diner]
Help me understand something here though. The SPC-1 disclosure report states you used "mirroring" as the data protection mechanism. That implies RAID 1 or 10. If so, how can you possibly claim more than 50% utilization?
- [Bistro Manager]
Yes we used mirroring. The utilization is based on used capacity as a percentage of the volume's exported capacity. The ratio of used capacity to raw available capacity is 44%.
Voila! 83% is actually 44%!
Good on you, Marc. Your answer is the one that I was expecting; less than 50%. Straight answer.
But as for the press release, I don't understand how claiming 83% capacity utilization for this benchmark -- with no explanation -- is anywhere near honest.
Most people will assume that they got this with much less performant RAID-5 given the >50% capacity utilization.
Readers of the press release are going to be
- impressed and wrong in their impression (83% of readers)
- confused like me (the remaining 44%)
My advice? When you next get a bill from 3PAR for anything, whether it be storage or a 3 course meal, query it. Every line item. Then get Marc Farley to check it over one last time for you.
He'll make sure you don't pay twice.
.
