Emerging non-volatile memory (NVM) technologies have DRAM-like latency with storage-like density, offering unique capability to analyze large data sets significantly faster than flash or disk storage. However, the hybrid nature of these NVM technologies such as phase-change memory (PCM) make it difficult to use them to best advantage in the memory-storage hierarchy. These NVMs lack the fast write latency required of DRAM and are thus not suitable as DRAM equivalent on the memory bus, yet their low latency even in random access patterns is not easily exploited over an I/O bus. In this work, we describe an FPGA-based system to execute application-specific operations in the NVM controller and evaluate its performance on two microbenchmarks and a keyvalue store. Our system Minerva1extends the conventional solidstate drive (SSD) architecture to offload data or I/O intensive application code to the SSD to exploit the low latency and high internal bandwidth of NVMs. Performing computation in the FPGA-based NVM storage controller significantly reduces data traffic between the host and storage and serves as an offload engine for data analysis workloads. A runtime library enables the programmer to offload computations to the SSD without dealing with the complications of the underlying architecture and inter-controller communication management. We have implemented a prototype of Minerva on the BEE3 FPGA system. We compare the performance of Minerva to a state of the art PCIe-attached PCM-based SSD. Minerva improves performance by an order of magnitude on two microbenchmarks. Minerva based key-value store performs up to 5.2 M get operations/s and 4.0 M set operations/s which is 7.45× and 9.85× higher than the PCM-based SSD that uses the conventional I/O architecture. This huge improvement comes from the reduction of data transfer between the storage to the host and the FPGA-based data processing in the SSD.

Emerging fast, non-volatile memories (e.g., phase change memories, spin-torque MRAMs, and the memristor) reduce storage access latencies by an order of magnitude compared to state-of-the-art flash-based SSDs. This improved performance means that software overheads that had little impact on the performance of flash-based systems can present serious bottlenecks in systems that incorporate these new technologies. We describe a novel storage hardware and software architecture that nearly eliminates two sources of this overhead: Entering the kernel and performing file system permission checks. The new architecture provides a private, virtualized interface for each process and moves file system protection checks into hardware. As a result, applications can access file data without operating system intervention, eliminating OS and file system costs entirely for most accesses. We describe the support the system provides for fast permission checks in hardware, our approach to notifying applications when requests complete, and the small, easily portable changes required in the file system to support the new access model. Existing applications require no modification to use the new interface. We evaluate the performance of the system using a suite of microbenchmarks and database workloads and show that the new interface improves latency and bandwidth for 4 KB writes by 60% and 7.2x, respectively, OLTP database transaction throughput by up to 2.0x, and Berkeley-DB throughput by up to 5.7x. A streamlined asynchronous file IO interface built to fully utilize the new interface enables an additional 5.5x increase in throughput with 1 thread and 2.8x increase in efficiency for 512 B transfers.

Emerging non-volatile memory technologies such as phase change memory (PCM) promise to increase storage system performance by a wide margin relative to both conventional disks and flash-based SSDs. Realizing this potential will require significant changes to the way systems interact with storage devices as well as a rethinking of the storage devices themselves. This paper describes the architecture of a prototype PCIe-attached storage array built from emulated PCM storage called Moneta. Moneta provides a carefully designed hardware/software interface that makes issuing and completing accesses atomic. The atomic management interface, combined with hardware scheduling optimizations, and an optimized storage stack increases performance for small, random accesses by 18x and reduces software overheads by 60%. Moneta array sustain 2.8~GB/s for sequential transfers and 541K random 4~KB~IO operations per second (8x higher than a state-of-the-art flash-based SSD). Moneta can perform a 512-byte write in 9~us (5.6x faster than the SSD). Moneta provides a harmonic mean speedup of 2.1x and a maximum speed up of 9x across a range of file system, paging, and database workloads. We also explore trade-offs in Moneta's architecture between performance, power, memory organization, and memory latency.

Emerging storage technologies such as flash memories, phase-change memories, and spin-transfer torque memories are poised to close the enormous performance gap between disk-based storage and main memory. We evaluate several approaches to integrating these memories into computer systems by measuring their impact on IO-intensive, database, and memory-intensive applications. We explore several options for connecting solid-state storage to the host system and find that the memories deliver large gains in sequential and random access performance, but that different system organizations lead to different performance trade-offs. The memories provide substantial application-level gains as well, but overheads in the OS, file system, and application can limit performance. As a result, fully exploiting these memories' potential will require substantial changes to application and system software. Finally, paging to fast non-volatile memories is a viable option for some applications, providing an alternative to expensive, powerhungry DRAM for supporting scientific applications with large memory footprints.