How i learned to stop worrying and love flash endurance

Abstract

Flash memory in Solid-State Disks (SSDs) has gained tremendous popularity in recent years. The performance and power benefits of SSDs are especially attractive for use in data centers, whose workloads are I/O intensive. However, the apparent limited write-endurance of flash memory has posed an impediment to the wide deployment of SSDs in data centers. Prior architecture and system level studies of flash memory have used simplistic endurance estimates derived from datasheets to highlight these concerns. In this paper, we model the physical processes that affect endurance, which include both stresses to the memory cells as well as a recovery process. Using this model, we show that the recovery process, which the prior studies did not consider, significantly boosts flash endurance. Using a set of real enterprise workloads, we show that this recovery process allows for orders of magnitude higher number of writes and erases than those given in datasheets. Our results indicate that SSDs that use standard wear-leveling techniques are much more resilient under realistic operating conditions than previously assumed and serve to explain some trends observed in recent flash measurement studies.