CATA: A Garbage Collection Scheme for Flash Memory File Systems

The problem of flash memory is that it cannot be overwritten unless erased in advance. In order to avoid having to erase during every update, non-in-place-update schemes have been widely used. In case of non-in-place update mechanism, garbage collection is needed to reclaim the obsolete space. In this paper, we study a new garbage collection scheme to reduce its cost such as the number of erase operations and the number of data copies. The proposed scheme determines the victim blocks by exploiting usage information of data blocks such as age, utilization and erase count. In addition, the proposed scheme predicts the future I/O workload and controls the number of victims to avoid disturbing the normal I/O operations. Experimental results show that the proposed scheme can perform well especially when the degree of locality is high.