Dispersed storage is really the key component of cloud storage architecture. The ability to, via policy, have data replicated throughout a distributed storage infrastructure is critical. This allows a service provider to offer storage services based on the level of the users subscription or the popularity of the item.
An example of a subscription-level policy could be a photo sharing site where a "paid membership" would make sure you have copies of your photos on three or four cloud storage pods elsewhere in the world while a "free membership" will only have a copy of your photo's on a single cloud storage pod. The difference is how much are you willing to pay to make sure that your photos are available to you if the cloud storage pod with your photos suffers a failure. With the paid membership, you are covered no matter what.
Another example would be the hot new single that is available for download -- iinitial release will see thousands of download requests and then they will taper off over time. The last thing you want to do is slow down your customer's ability to purchase something, but at a dollar a song you don't want to waste your profits on excess storage. In a dispersed model you could, again through policy, put the song on 20 different cloud storage pods spread throughout the world. Then, as the interest dies down, contract its dispersion to one plus a DR.
A key component of dispersion is automation so that you can control how your data objects are dispersed without having to be manually involved in each object. Cloud storage has to deal with very large storage capacities and a very high number of storage objects being managed by very few administrators so the service can be offered to consumers or internal employees at very low costs. This is why the policy-driven nature of dispersed cloud storage becomes critical.
Automation of this dispersion based on policies is not only critical in keeping costs down; it is a key to survival. As cloud providers begin to deal with millions and billions of objects, managing them discreetly becomes nearly impossible. Policies are going to be required that will track files based on user or usage during the entire life cycle of the file.
In our next entry we will discuss the next key element: balanced modularity.
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George Crump is founder of Storage Switzerland, an analyst firm focused on the virtualization and storage marketplaces. It provides strategic consulting and analysis to storage users, suppliers, and integrators. An industry veteran of more than 25 years, Crump has held engineering and sales positions at various IT industry manufacturers and integrators. Prior to Storage Switzerland, he was CTO at one of the nation's largest integrators.