A Survey on the Integration of NAND Flash Storage in the Design of File Systems and the Host Storage Software Stack

With the ever-increasing amount of data generate in the world, estimated to reach over 200 Zettabytes by 2025, pressure on efficient data storage systems is intensifying. The shift from HDD to flash-based SSD provides one of the most fundamental shifts in storage technology, increasing performance capabilities significantly. However, flash storage comes with different characteristics than prior HDD storage technology. Therefore, storage software was unsuitable for leveraging the capabilities of flash storage. As a result, a plethora of storage applications have been design to better integrate with flash storage and align with flash characteristics. In this literature study we evaluate the effect the introduction of flash storage has had on the design of file systems, which providing one of the most essential mechanisms for managing persistent storage. We analyze the mechanisms for effectively managing flash storage, managing overheads of introduced design requirements, and leverage the capabilities of flash storage. Numerous methods have been adopted in file systems, however prominently revolve around similar design decisions, adhering to the flash hardware constrains, and limiting software intervention. Future design of storage software remains prominent with the constant growth in flash-based storage devices and interfaces, providing an increasing possibility to enhance flash integration in the host storage software stack

A Survey on the Integration of NAND Flash Storage in the Design of File Systems and the Host Storage Software Stack

With the ever-increasing amount of data generate in the world, estimated to reach over 200 Zettabytes by 2025, pressure on efficient data storage systems is intensifying. The shift from HDD to flash-based SSD provides one of the most fundamental shifts in storage technology, increasing performance capabilities significantly. However, flash storage comes with different characteristics than prior HDD storage technology. Therefore, storage software was unsuitable for leveraging the capabilities of flash storage. As a result, a plethora of storage applications have been design to better integrate with flash storage and align with flash characteristics. In this literature study we evaluate the effect the introduction of flash storage has had on the design of file systems, which providing one of the most essential mechanisms for managing persistent storage. We analyze the mechanisms for effectively managing flash storage, managing overheads of introduced design requirements, and leverage the capabilities of flash storage. Numerous methods have been adopted in file systems, however prominently revolve around similar design decisions, adhering to the flash hardware constrains, and limiting software intervention. Future design of storage software remains prominent with the constant growth in flash-based storage devices and interfaces, providing an increasing possibility to enhance flash integration in the host storage software stack

Dynamic Binary Translation for Embedded Systems with Scratchpad Memory

Embedded software development has recently changed with advances in computing. Rather than fully co-designing software and hardware to perform a relatively simple task, nowadays embedded and mobile devices are designed as a platform where multiple applications can be run, new applications can be added, and existing applications can be updated. In this scenario, traditional constraints in embedded systems design (i.e., performance, memory and energy consumption and real-time guarantees) are more difficult to address. New concerns (e.g., security) have become important and increase software complexity as well. In general-purpose systems, Dynamic Binary Translation (DBT) has been used to address these issues with services such as Just-In-Time (JIT) compilation, dynamic optimization, virtualization, power management and code security. In embedded systems, however, DBT is not usually employed due to performance, memory and power overhead. This dissertation presents StrataX, a low-overhead DBT framework for embedded systems. StrataX addresses the challenges faced by DBT in embedded systems using novel techniques. To reduce DBT overhead, StrataX loads code from NAND-Flash storage and translates it into a Scratchpad Memory (SPM), a software-managed on-chip SRAM with limited capacity. SPM has similar access latency as a hardware cache, but consumes less power and chip area. StrataX manages SPM as a software instruction cache, and employs victim compression and pinning to reduce retranslation cost and capture frequently executed code in the SPM. To prevent performance loss due to excessive code expansion, StrataX minimizes the amount of code inserted by DBT to maintain control of program execution. When a hardware instruction cache is available, StrataX dynamically partitions translated code among the SPM and main memory. With these techniques, StrataX has low performance overhead relative to native execution for MiBench programs. Further, it simplifies embedded software and hardware design by operating transparently to applications without any special hardware support. StrataX achieves sufficiently low overhead to make it feasible to use DBT in embedded systems to address important design goals and requirements

Elevating commodity storage with the SALSA host translation layer

To satisfy increasing storage demands in both capacity and performance, industry has turned to multiple storage technologies, including Flash SSDs and SMR disks. These devices employ a translation layer that conceals the idiosyncrasies of their mediums and enables random access. Device translation layers are, however, inherently constrained: resources on the drive are scarce, they cannot be adapted to application requirements, and lack visibility across multiple devices. As a result, performance and durability of many storage devices is severely degraded. In this paper, we present SALSA: a translation layer that executes on the host and allows unmodified applications to better utilize commodity storage. SALSA supports a wide range of single- and multi-device optimizations and, because is implemented in software, can adapt to specific workloads. We describe SALSA's design, and demonstrate its significant benefits using microbenchmarks and case studies based on three applications: MySQL, the Swift object store, and a video server.Comment: Presented at 2018 IEEE 26th International Symposium on Modeling, Analysis, and Simulation of Computer and Telecommunication Systems (MASCOTS

Executing Hard Real-Time Programs on NAND Flash Memory Considering Read Disturb Errors

학위논문 (석사)-- 서울대학교 대학원 공과대학 컴퓨터공학부, 2017. 8. 이창건.죄근 IoT 와 임베디드 시스템에 대한 관심이 급증하면서 NAND 플래쉬 메모리를 사용하는 장치들 또한 증가하고 있다. 이러한 장치들은 NAND 플래시 메모리를 사용함으로써 큰 이득을 얻을 수 있지만 여전히 신뢰성 측면에서는 해결되지 않은 이슈들이 있다. 본 논문에서는 이러한 신뢰성 문제를 극복할 수 있는 방안에 대해 논의한다. NAND 플래쉬 메모리는 각 페이지에 대해 읽기 명령을 반복적으로 수행 할 있는 물리적 회수가 한정되어 있기 때문에 읽기 횟수가 한계치에 도달하기 전에 재할당을 해주어야 하는 문제가 있다. 본 논문에서는 프로그램 코드가 저장되어 있는 read-only 페이지를 읽어 코드를 수행하는 실시간 임베디드 시스템에서 실시간 제약 조건을 만족하면서 재할당을 하여 READ DISTURB ERROR 를 줄이는 기법에 대해 제안한다. 본 논문에서 제안하는 기법을 구현하고 실험함으로써, NAND 플래쉬 메모리의 읽기 한계치에 도달하기 전에 재할당이 보장됨을 보인다. 또한 제안하는 기법을 사용 할 경우 요구되는 RAM 크기가 최대 48% 감소함을 확인한다1 Introduction 1 2 Related works 6 3 Background and problem description 10 3.1 NAND flash memory 10 3.2 HRT-PLRU 13 3.3 Reliability issues of the NAND flash memory 18 3.4 Problem description 28 3.5 System notation 30 4 Approach 31 4.1 Per-task analysis 31 4.2 Convex optimization 37 5 Evaluation 41 6 Future works 46 7 Conclusion 47 Summary (Korean) 48 References 49Maste

HBM: A hybrid buffer management scheme for solid state disks

Master'sMASTER OF SCIENC