Key-value stores are widely used as storage backends, due to their simple, yet flexible interface for cache, storage, file system, and database systems. However, when used with high performance NVMe devices, their high compute requirements for data management often leave the device bandwidth under-utilized. This leads to a performance mismatch of what the device is capable of delivering and what it actually delivers, and the gains derived from high speed NVMe devices is nullified. In this paper, we introduce KV-SSD (Key-Value SSD) as a key technology in a holistic approach to overcome such performance imbalance. KV-SSD provides better scalability and performance by simplifying the software storage stack and consolidating redundancy, thereby lowering the overall CPU usage and releasing the memory to user applications. We evaluate the performance and scalability of KV-SSDs over state-of-the-art software alternatives built for traditional block SSDs. Our results show that, unlike traditional key-value systems, the overall performance ofKV-SSD scales linearly, and delivers 1.6 to 57x gains depending on the workload characteristics.

Performance critical transaction and storage systems require fast persistence of write data. Typically, a non-volatile RAM (NVRAM) is employed on the datapath to the permanent storage, to temporarily and quickly store write data before the system acknowledges the write request. NVRAM is commonly implemented with battery-backed DRAM. Unfortunately, battery-backed DRAM is small and costly, and occupies a precious DIMM slot. In this paper, we make a case for dual, byte- and block-addressable solid-state drive (2B-SSD), a novel NAND flash SSD architecture designed to offer a dual view of byte addressability and traditional block addressability at the same time. Unlike a conventional storage device, 2B-SSD allows accessing the same file with two independent byte- and block-I/O paths. It controls the data transfer between its internal DRAM and NAND flash memory through an intuitive software interface, and manages the mapping of the two address spaces. 2B-SSD realizes a wholly different way and speed of accessing files on a storage device; applications can access them directly using memory-mapped I/O, and moreover write with a DRAM-like latency. To quantify the benefits of 2B-SSD, we modified logging subsystems of major database engines to store log records directly on it without buffering them in the host memory. When running popular workloads, we measured throughput gains in the range of 1.2X and 2.8X with no risk of data loss.

This paper presents YourSQL , a database system that accelerates data-intensive queries with the help of additional in-storage computing capabilities. YourSQL realizes very early filtering of data by offloading data scanning of a query to user-programmable solid-state drives. We implement our system on a recent branch of MariaDB (a variant of MySQL). In order to quantify the performance gains of YourSQL, we evaluate SQL queries with varying complexities. Our result shows that YourSQL reduces the execution time of the whole TPC-H queries by 3.6×, compared to a vanilla system. Moreover, the average speed-up of the five TPC-H queries with the largest performance gains reaches over 15×. Thanks to this significant reduction of execution time, we observe sizable energy savings. Our study demonstrates that the YourSQL approach, combining the power of early filtering with end-to-end datapath optimization, can accelerate large-scale analytic queries with lower energy consumption.