Towards a Scalable and Write-Free Multi-version Checkpointing Scheme in Solid State Drives

Flash memory based solid state drives (SSDs) are widely adopted in mobile devices, PCs and data centers, making their reliability critical. Although periodically creating checkpoints is a well-developed technique for traditional hard disk drives, very few work has exploited the unique properties of SSDs to accelerate checkpoint creation and reduce storage cost. More specifically, the remap-on-write property of SSD creates a trail of multiple versions of data, which can be exploited to create multiple checkpoints without engendering extra writes. However, efficiently managing the metadata to support multiple checkpoints is challenging. In this paper, we propose a low storage cost and high performance scheme to support multiple checkpoints in SSDs. Instead of storing a log-based snapshot of the entire Flash Translation Layer (FTL) per checkpoint, we efficiently keep track of the changes to the FTL across multiple checkpoints, thus accelerating the creation, deletion, and activation of checkpoints within minimum storage overhead and minimum impact on regular SSD operations. Experiments on Microsoft real-world benchmarks confirm the advantage of the proposed scheme over a fully snapshot scheme in terms of storage and performance overhead.