You are not correct, it is _not_ a cache but instead something that provides the union of storage between two drives. Remember, the examples have stuff _only_ o

You are not correct, it is _not_ a cache but instead something that provides the union of storage between two drives. Remember, the examples have stuff _only_ on the SSD. Instead, this appears to be an implementation of so-called "tiered storage". This is novel in that is the first time such an approach has been applied to consumer grade solutions. Usually, one might find tiered storage as part of an extremely expensive solution that EMC might give you as part of an elaborate storage system.