The Effect of Absorbing Hot Write References on FTLs for Flash Storage Supporting High Data Integrity

Abstract

Flash storages are prevalent as portable storage in comput- ing systems. When we consider the detachability of Flash storage devices, data integrity becomes an important issue. We consider the performance of Flash Translation Layer (FTL) schemes in conjunction with ¯le system behavior that pursue high data integrity. To assure extreme data integrity, ¯le systems synchronously write all ¯le data to storage ac- companying hot write references. In this study, 1) we con- centrate on the e®ect of hot write references on Flash stor- age, and 2) we consider the e®ect of absorbing the hot write references via nonvolatile write cache on the performance of the FTL schemes in Flash storage. In so doing, we quantify the performance of typical FTL schemes for workloads that contain hot write references through a wide range of exper- iments on a real system environment. Results show that for workloads with hot write references FTL performance does not conform with previously reported studies. We also conclude that the impact of the underlying FTL schemes on the performance of Flash storage is dramatically reduced by absorbing the hot write references via nonvolatile write cache.