Improving CPU I/O Performance via SSD Controller FTL Support for Batched Writes

Exploiting a storage hierarchy is critical to cost-effective data management. One can achieve great performance when working solely on main memory data. But this comes at a high cost. Systems that use secondary storage as the "home" for data have much lower storage costs as they can not only make the data durable but reduce its storage cost as well. Performance then becomes the challenge, reflected in an increased execution cost. Log structured stores, e.g. Deuteronomy, improve I/O cost/performance by batching writes. However, this incurs the cost of host-based garbage collection and recovery, which duplicates SSD flash translation layer (FTL) functionality. This paper describes the design and implementation in a controller for an Open Channel SSD of a new FTL that supports multi-page I/O without host-based log structuring. This both simplifies the host system and improves performance. The new FTL improves I/O cost/performance with only modest change to the current block at a time, update-in-place interface.