This research is to design a new buffer cache for flash memory storage systems. Specifically, flash memory based storage systems are compact and fast, compared with the traditional hard disks. Eventually, flash memory based solid state disks (SSDs) became another attractive storage unit, to be applied to general computing systems. However, flash memory based SSDs show critical drawbacks that stem from the unique characteristics of the electronic storage units, incurring huge overhead. Especially these drawbacks cause serious performance problem when the access pattern of overwrite operations is irregular. This is mainly because the irregular access pattern increases the frequency of overwrite operations and merge operations in the flash memory, which may cause serious overhead. In order to reduce such overhead, this paper proposes a new buffer cache, called the ML-ELFRU (Multi-Level Elaborate Least Frequently/Recently Used Buffer), for a flash translation layer (FTL) in flash memory storages or SSDs. Additionally, experiments are carried out to show that the ML-ELFRU can reduce the number of replacement operations in the buffer cache and the number of merge operations in the electronic storage unit compared with other existing buffer cache policies.