Sunday, February 28, 2010

Architecture versus Feature

I'll give NetApp CEO Tom Georgens credit for one thing, he knows how to stir the pot. There’s been lots of good and interesting debate over a feature offered by several storage suppliers since he made that comment.

Notice I used the word "feature" - that's an important distinction. Automated tiered storage (I'll say ATS as a generic term - Compellent calls it Data Progression, others have different marketing terms) is a feature built on top of an underlying storage architecture. Other features include thin provisioning, snapshots, replication, data protection and storage management. It's important to understand the foundation used to offer up features when deciding how functional and useful they really are in YOUR environment.

In many cases storage companies have developed ways to virtualize physical storage in order to treat the available installed disk capacity (or some subset of that capacity) as a single logical pool. Using this abstraction, volumes or LUNs can be created which ignore the limitations imposed by a single physical disk array (such as being able to change RAID protection levels on a LUN). Depending on the way in which storage has been virtualized the ability to deliver more value from the aforementioned features will be impacted.

For example, some virtualization schemes are built on top of existing, traditional array architectures which limit the level of granularity for virtualization. Be aware that any architecture with a long legacy will show signs of these limitations by restricting the utility of the newer features. By necessity, these legacy systems must maintain backwards compatibility with older generations so that services such as replication and storage management aren't "broken" which is a good thing. The trade off is a watered down capability for emerging feature sets. Sometimes this is because of hardware dependencies in earlier generations of products.

In the case of newer generation platforms, such as Compellent Storage Center, there is no such bolting on of new features and software engineers are free to implement these exciting new capabilities in more valuable ways.

For ATS, this means having the ability to create a logical volume which provides storage economy by addressing performance requirements without the cost penalty associated with locking the entire volume into high performance disk. For legacy architectures it means moving the entire volume around to address performance spikes while maintaining a reservation of storage in each tier for these volume moves. You can see there's a huge difference in the implementation between an ATS offering on one architecture versus another.

To REALLY understand how any of these features can help you, it's important to take the time to learn about the foundational architecture used to build these features. Take a look at Compellent's Fluid Data architecture and you'll see why we are perfectly suited to deliver advanced storage features in an easy to manage package.

Everyone sells to their strengths, which is why Mr. Georgens is trying to convince you that tiering is dying. By understanding what those strengths (and associated weaknesses) are you'll be better able to make the best decision on future storage purchases for your business.

Focus on architecture before you get sold on features.

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