Designing a Flash Translation Layer

Although flash memory has risen as a popular secondary storage medium, its performance is difficult to predict. The reason is that internally, flash memory is subject to a complex set of constraints. Storage units must be erased before they are updated, erases have a bigger granularity than writes, and each storage unit has a limited lifetime in terms of erases. A flash translation layer (FTL) hides these constraints and exposes a simple block interface to the application. The problem is that the FTL's behind-the-scene work impacts performance. In this presentation, we show how to redesign the FTL so as to eliminate an important performance bottlenecks and thereby make the performance of flash devices more predictable.