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January 15, 2009

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Bill

Marc-

I wouldn't try to overcomplicate it, but you are on the right track.

With 3PAR, chunklets are treated as really small, granular disks as you mentioned, and RAID is applied to the chunklets (in algorithms that give high availability by using different failure domains such as spindles, magazines, and even cages), and then volumes are created out of these RAID sets of chunklets via wide striping.

But you hit the most important point. A single FC drive can have hundreds or even thousands of chunklets. The array has hundreds of thousands of chunklets, which I like to think of as virtual spindles.

It's a very granular solution, and we humans as storage admins aren't required to map these little virtualized spindles together... the array software takes care of it for us in a way that is safe and efficient at the same time.

marc farley

Thanks Bill, I'm planning to pursue the points you raised over the course of several future postings. Wide striping is conceptually simple, but there are some very interesting details that I want to shed some light on. There's a growing interest in wide striping in the blogosphere.

Dave Vellante

Very cool video Mark and excellent explanation-- nice work. If I understand correctly, from a business standpoint, chunklets are an enabler for space efficient storage. The byproduct of chunklets is quantified here by David Floyer:
http://wikibon.org/?c=wiki&m=v&title=Case_Study%3A_Evaluating_the_virtualization_and_thin_provisioning_benefits_achieved_by_3PAR_customers#

And all this happens with no disruption to the application, correct? In the words of Darth Vader..."Impressive."

marc farley

Thanks Dave for your comment and the link to David Floyer's wiki piece!

I'm working on another video that shows the advantages of wide striping with chunklets. In general, chunklets are terrific for simultaneously scaling capacity AND performance.

To be clear, chunklets have an impact on utilization efficiently, but thin provisioning with "allocate on write" functionality is responsible for most of the utilization benefits people associate with 3PAR storage.

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