Back in the '90s, Gartner discussed tiered storage architecture with traditional storage arrays. Devices were tiered based on their cost and data on certain factors such as criticality, age, performance, and a few others. This meant that some data made their way to the fastest and most reliable tier and other data into slower and less expensive ones. This tiering was done at the device level, that is, the storage administrator segmented devices based on cost or there was heterogeneous storage presented to servers varying between high-end, mid-end, and low-end arrays. An administrator would then manually provision data on the respective tiers. There have been several advancements with storage arrays automating tiering at the array level.

With virtualization however, data seldom static and the ability to move data around through features such as Storage vMotion gave the right level of agility to the vSphere administrators. The flip side of this is that it became very...