US Patent 10496315 Unified tier and cache structure

A data storage system may include a first storage pool and a second storage pool, with the second storage pool comprising larger, slower storage drives. The data storage system may associate, with a first data, a first parameter corresponding to an access frequency for short term reads, a second parameter corresponding to access frequency for long term reads, a third parameter corresponding to an access frequency for short term writes, and a fourth parameter corresponding to an access frequency for long term writes. The data storage system may then determine whether to store the first data on the first storage pool or the second storage pool based on at least one of the first parameter, the second parameter, the third parameter, and the fourth parameter.