Thin provisioning has become prevalent in storage systems today. As a storage system feature, it has become expected to be present when the purchase of new storage is being considered by Information Technology professionals. Product offerings from vendors continue to highlight the economic gains from the improvement in storage efficiency with thin provisioning. Understanding of the value from thin provisioning in storage systems is moving beyond the mere presence of the feature to an evaluation of the implementation and the implications of the characteristics.
Allocating space on storage as data is written is the basic premise of thin provisioning. While this seems obvious, previously the entire amount of space was allocated whether it was used or not. This led to trapped and ineffectively used capacity. Thin provisioning, or allocating only on write demand, is a means to deal with the imperfect process for assigning storage. It also permits the capacity potential seen by applications and operating systems (a vestige of the expectation of having a set amount of capacity defined prior to actual use) to be greater than the actual physical available capacity.