Dataset Management-Aware Software Architecture for Storage Systems Based on SSDs

Solid-state drives (SSD) based on flash memory offer the opportunity to build high-performance storage systems with low energy consumption and high reliability. Crucial concerns of current SSDs are their write performance, especially for small random requests, and the limited lifespan of their flash memory. Both can be mitigated by providing an SSD with information about the stored data. This may include notifications about deal location of storage capacity or the prevalent access type. Knowing the size, latency requirements and type of upcoming requests can help to improve the dataset management (DSM) of an SSD allowing further performance improvement and memory lifetime extension. Often such information has to be passed through intermediate layers (e.g., RAIDs) placed between the information sources (e.g., file system) and the information sinks (i.e., the SSDs). Problems arise because such layers often do not appropriately propagate DSM commands making the intended optimizations unfeasible. In this paper, we propose a file system-independent, layered I/O software architecture that enables the handling of DSM commands throughout all of the layers. Moreover, it allows to address cross-cutting concerns related to the propagation of DSM commands. Its applicability is demonstrated by an exemplary instance based on stacked software RAID layers. The results of an experimental evaluation based on Linux Software RAID clearly show the benefits of the proposed architecture.