Application-Aware and Software-Defined SSD Scheme for Tencent Large-Scale Storage System

Tencent, one of the biggest Internet companies in China, contains billions of users and over 600-PB data, and leverages thousands of SSDs in the storage system to improve system performance and obtain energy savings. Existing commercial SSDs however fail to meet the needs of the ultra largescale applications due to not matching the service patterns. In order to address this problem and deliver high performance, we propose an application-aware and software-defined SSD scheme for Tencent applications, called TSSD. TSSD explores and exploits the business characteristics of Tencent, which facilitates the efficient use of SSDs. TSSD is software-defined by packaging each flash chip as a fully independent and concurrent storage unit. Each concurrent unit can be mounted as a character device, which allows the application layer to manage the flash chips in a more efficient manner, while optimizing the data layout. TSSD further employs a host-target FTL (TFTL) that uses a dedicated interface in the application layer, which efficiently connects the application layer with flash chips. Application layer hence becomes more accurately by using the flash memory chip-level information from TFTL, including the storage utilization, the degree of wear, etc. Moreover, TFTL is a programmable FTL and provides a programmable interface to the application layer. According to the running states of SSDs and workload information, TSSD makes use of the programmable interface to efficiently improve the performance of the FTL, wear leveling, and garbage collection for the specified applications. Extensive experiments use the real-world datasets from the commercial storage systems of Tencent. The results demonstrate that TSSD significantly improves the storage system performance and meets the needs of the Tencents large-scale business applications.