A real-time flash translation layer via adaptive partial garbage collection

In real-time embedded systems with flash storage memory, partial garbage collection is used to avoid long response latency and provide guaranteed response time upper bound. However, existing partial garbage collection schemes involve too many valid page copy and erase operations, which results in degradation in both system average performance and endurance of flash memory. To solve this problem, in this paper, we propose a real-time hybrid-level flash translation layer (FTL) called RAFTL – a real-time FTL using an adaptive partial garbage collection policy. RAFTL allocates physical blocks mapped to the same logical block on demand to postpone the partial garbage collection process. Moreover, we adopt an adaptive partial garbage collection policy, which combines the centralised and the distributed partial garbage collection policies. The experimental results show that our scheme reduces the valid page copy and erase operations significantly. Also, on the basis of providing a guaranteed worst case system response time, RAFTL provides an average write request response time which is approximate to the time to write one page.