Read leveling for flash storage systems

Abstract

Due to its several attractive benefits such as shock resistance, energy efficiency, and space-efficient form factor, flash memory is now applied to a wide range of electronics. Typically, since write requests are harmful to the health of flash memory, some flash-based storage devices tend to be deployed for read-intensive applications recently. However, as the technology node keeps going, read disturbance becomes a worsening problem in flash memory. Even under a pure read workload, flash memory often needs to refresh disturbed data, which brings about additionalwrite and erase operations. In this work, we propose a new design direction, read leveling, that aims at distributing read-hot data over different flash blocks. Thus, all read operations could be issued to different blocks as evenly as possible, so as to minimize the interference between read-hot data and other valid data on the same block and avoid refreshing cost. A series of experiments were conducted to prove the effectiveness of the proposed concept, and the results are very encouraging.