Abstract: Recently, solid-state drives (SSDs) have been used in a wide range of emerging data processing systems. Essentially, an SSD is a complex embedded system that involves both hardware and software design. For the latter, firmware modules such as the flash translation layer (FTL) orchestrate internal operations and flash management, and are crucial to the overall input/output performance of an SSD. Despite the rapid development of new SSD features in the market, the research of flash firmware has been mostly based on simulations due to the lack of a realistic and extensible SSD development platform. In this paper, we propose SoftSSD, a software-oriented SSD development platform for rapid flash firmware prototyping. The core of SoftSSD is a novel framework with an event-driven programming model. With the programming model, new FTL algorithms can be implemented and integrated into a full-featured flash firmware in a straightforward way. The resulting flash firmware can be deployed and evaluated on a hardware development board, which can be connected to a host system via peripheral component interconnect express and serve as a normal non-volatile memory express SSD. Different from existing hardware-oriented development platforms, SoftSSD implements the majority of SSD components (e.g., host interface controller) in software, so that data flows and internal states that were once confined in the hardware can now be examined with a software debugger, providing the observability and extensibility that are critical to the rapid prototyping and research of flash firmware. We describe the programming model and hardware design of SoftSSD. We also perform experiments with real application workloads on a prototype board to demonstrate the performance and usefulness of SoftSSD, and release the open-source code of SoftSSD for public access.

基于SoftSSD的快速固态硬盘固件原型开发

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