What’s the Difference Between Tiering and Caching?

While “storage tiering” and “caching” are often used interchangeably, especially when discussing flash media, they are actually two different processes with different definitions. “Tiered data” resides on one media but moves between media as patterns of data access change. “Caching” places a copy of data on a high-performance mechanism like solid-state memory or dynamic RAM in order to improve performance. Cached data ultimately also resides on a lower storage tier like a hard-disk drive, while tiered storage moves data to a different storage mechanism and selects a location that adjusts availability, performance, and cost of storing the data.