1. A method comprising: when it is determined that cache memory in a storage system has reached a capacity threshold, associating each of a plurality of data dictionary entries stored in the cache memory with a respective merge identifier, each data dictionary entry corresponding with a respective data chunk, each data dictionary entry indicating a storage location of the respective data chunk in the storage system, the respective merge identifier indicating temporal locality information about the respective data chunk; and storing the plurality of data dictionary entries to disk memory in the storage system, each of the stored plurality of data dictionary entries including the respective merge identifier.