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An introduction to thin provisioning

One of the more important but often misunderstood advancements within data storage is thin provisioning. This article defines and discusses thin provisioning, its economic impact and how it works.

System administrators typically provide themselves with more storage than is needed for various applications -- planning ahead for growth. An application may have 100 GB of actual data, but based on some analysis or at the request of the business unit or department, the system administrator creates a volume that has 500 GB of capacity allowing for data growth. When the volume is created this 500 GB is allocated and dedicated to that application and no other application can use it. However, in many cases the full 500 GB is never used and is essentially wasted. This is a major problem with managing storage capacity and is often referred to as stranded storage.

The inefficiencies of traditional storage provisioning can negatively impact capital costs and storage administration resources. The most obvious issue is the amount of storage that becomes unused and therefore increases the total cost of ownership. Additionally, since this allocated but unused storage capacity cannot be reclaimed for other applications, customers have to buy more storage capacity as their environments grow, increasing cost even further. At some point, customers may actually be required to buy a completely new storage system in addition to the one they have in place. ESG did a rapid survey in June 2005 of 20 customers that focused on the limitations of traditional storage provisioning methods. The highlights of that survey included:

  • 54% of the customers were aware that they had stranded and unused storage capacity due to inefficient provisioning methods.
  • 55% of these customers had between 31-50% of stranded and unused storage. For example, if they had 10 TB of storage capacity then 3.1- 5 TB was stranded.
  • 45% of the total users had to buy an additional storage system because they could not utilize their stranded storage. This means that although these customers had unused storage capacity theyhad already paid for, they needed to buy a new storage system to meet the needs of their business.
  • 30% of users are planning to buy an additional storage system in the next 12 months because they cannot access their stranded storage. Combining the 45% of customers that purchased an additional storage system with the 30% that are planning to buy, the number increases to 75%.
  • 80% of users felt that storage provisioning was a time and resource drain on their IT organizations.

The following are some of the ways that thin provisioning can save customers money:

Less storage is required initially when purchasing a new storage system. Using traditional storage provisioning methods, customers have no choice but to buy additional capacity up front. However, with thin provisioning, this is not required since capacity does not have to be pre-allocated. A customer that previously had to buy 10 TB of capacity, because of the limitations of traditional provisioning, can instead acquire 2.5 TB or 5 TB, due to the more efficient thin provisioning method.

Since there is no longer any stranded storage capacity, less storage is required over the life of the storage system.Customers have a large amount of stranded and unused capacity due to the inefficiencies of traditional provisioning methods. The wasted cost of stranded storage is eliminated with thin provisioning.

Additional storage systems will not be required based on having stranded storage. Every storage system has a finite amount of storage capacity that it can support. When the storage system has reached its optimal capacity then customers may need to implement an additional storage system. Acquiring a completely new storage system because of stranded storage is extremely wasteful.

More servers per storage system providing greater levels of consolidation. As described above, since capacity doesn't have to be dedicated and fixed on a per-volume basis with thin provisioning, customers can create more volumes. As a result, more servers can be attached to a single storage system. Storage consolidation is a major initiative and thin provisioning can enable even greater levels of consolidation.

Thin provisioning is "just in time capacity" that essentially eliminates allocated but unused storage or stranded storage. It also greatly simplifies storage provisioning tasks reducing administration costs. Customers should look at storage systems that support thin provisioning differently than those that do not when evaluating the initial capacity configuration, budgeting and planning capacity growth over time and the total cost of ownership.

The economic impact of thin provisioning can be substantial, saving literally thousands, tens of thousands and potentially hundreds of thousands of dollars depending on the scope of the environment.

About the author: Tony Asaro is the senior analyst for Enterprise Strategy Group.

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