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, the data dictionary entries stored to disk at the same time sharing the same merge identifier, the merge identifier indicating when the data dictionary entries were stored to disk.