Exploring Design Dimensions in Flash-based Mass-memory Devices

Mission-critical space system applications present several issues: a typical one is the design of a mass-memory device (i.e., a solid- state recorder). This goal could be accomplished by using flash- memories: the exploration of a huge number of parameters and trade-offs is needed. On the one hand flash-memories are nonvolatile, shock-resistant and power-economic, but on the other hand their cost is higher than normal hard disk, the number of erasure cycles is bounded and other different drawbacks have to be considered. In addition space environment presents various issues especially because of radiations: the design of a flash- memory based solid-state recorder implies the exploration of different and quite often contrasting dimensions. No systematic approach has so far been proposed to consider them all as a whole: as a consequence the design of flash-based mass-memory device for space applications is intended to be supported by a novel design environment currently under development and refinemen

Flash-memories in Space Applications: Trends and Challenges

Nowadays space applications are provided with a processing power absolutely overcoming the one available just a few years ago. Typical mission-critical space system applications include also the issue of solid-state recorder(s). Flash-memories are nonvolatile, shock-resistant and power-economic, but in turn have different drawbacks. A solid-state recorder for space applications should satisfy many different constraints especially because of the issues related to radiations: proper countermeasures are needed, together with EDAC and testing techniques in order to improve the dependability of the whole system. Different and quite often contrasting dimensions need to be explored during the design of a flash-memory based solid- state recorder. In particular, we shall explore the most important flash-memory design dimensions and trade-offs to tackle during the design of flash-based hard disks for space application

SimpleSSD: Modeling Solid State Drives for Holistic System Simulation

Existing solid state drive (SSD) simulators unfortunately lack hardware and/or software architecture models. Consequently, they are far from capturing the critical features of contemporary SSD devices. More importantly, while the performance of modern systems that adopt SSDs can vary based on their numerous internal design parameters and storage-level configurations, a full system simulation with traditional SSD models often requires unreasonably long runtimes and excessive computational resources. In this work, we propose SimpleSSD, a highfidelity simulator that models all detailed characteristics of hardware and software, while simplifying the nondescript features of storage internals. In contrast to existing SSD simulators, SimpleSSD can easily be integrated into publicly-available full system simulators. In addition, it can accommodate a complete storage stack and evaluate the performance of SSDs along with diverse memory technologies and microarchitectures. Thus, it facilitates simulations that explore the full design space at different levels of system abstraction.Comment: This paper has been accepted at IEEE Computer Architecture Letters (CAL

Dynamic Virtual Page-based Flash Translation Layer with Novel Hot Data Identification and Adaptive Parallelism Management

Solid-state disks (SSDs) tend to replace traditional motor-driven hard disks in high-end storage devices in past few decades. However, various inherent features, such as out-of-place update [resorting to garbage collection (GC)] and limited endurance (resorting to wear leveling), need to be reduced to a large extent before that day comes. Both the GC and wear leveling fundamentally depend on hot data identification (HDI). In this paper, we propose a hot data-aware flash translation layer architecture based on a dynamic virtual page (DVPFTL) so as to improve the performance and lifetime of NAND flash devices. First, we develop a generalized dual layer HDI (DL-HDI) framework, which is composed of a cold data pre-classifier and a hot data post-identifier. Those can efficiently follow the frequency and recency of information access. Then, we design an adaptive parallelism manager (APM) to assign the clustered data chunks to distinct resident blocks in the SSD so as to prolong its endurance. Finally, the experimental results from our realized SSD prototype indicate that the DVPFTL scheme has reliably improved the parallelizability and endurance of NAND flash devices with improved GC-costs, compared with related works.Peer reviewe

Analysis of The Typical Performance Routines for Recovering Data from Solid State Drive During a Forensic Acquisition

Analysis of The Typical Performance Routines for Recovering Data from Solid State Drive During a Forensic Acquisitio

On the use of NAND flash memory in high-performance relational databases

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2008.Includes bibliographical references (p. 47-49).High-density NAND flash storage has become relatively inexpensive due to the popularity of various consumer electronics. Recently, several manufacturers have released IDE-compatible NAND flash-based drives in sizes up to 64 GB at reasonable (sub-$1000) prices. Because flash is significantly more durable than mechanical hard drives and requires considerably less energy, there is some speculation that large data centers will adopt these devices. As database workloads make up a substantial fraction of the processing done by data centers, it is interesting to ask how switching to flash-based storage will affect the performance of database systems. We evaluate this question using IDE-based flash drives from two major manufacturers. We measure their read and write performance and find that flash has excellent random read performance, acceptable sequential read performance, and quite poor write performance compared to conventional IDE disks. We then consider how standard database algorithms are affected by these performance characteristics and find that the fast random read capability dramatically improves the performance of secondary indexes and index-based join algorithms. We next investigate using logstructured filesystems to mitigate the poor write performance of flash and find an 8.2x improvement in random write performance, but at the cost of a 3.7x decrease in random read performance. Finally, we study techniques for exploiting the inherent parallelism of multiple-chip flash devices, and we find that adaptive coding strategies can yield a 2x performance improvement over static ones. We conclude that in many cases flash disk performance is still worse than on traditional drives and that current flash technology may not yet be mature enough for widespread database adoption if performance is a dominant factor. Finally, we briefly speculate how this landscape may change based on expected performance of next-generation flash memories.by Daniel Myers.S.M

Theory and practice of flash memory mobile forensics

This paper is an introduction to flash memory forensics with a special focus on completeness of evidence acquired from mobile phones. Moving through academic papers and industrial documents will be introduced the particular nature of non-volatile memories present in nowadays mobile phones; how they really work and which challenges they pose to forensic investigators. Then will be presented an advanced test in which some brand new flash memories have been used to hide data in man-made bad blocks: the aim is to verify if forensic software tools are able to acquire data from such blocks, and to evaluate the possibility to hide data at analysts’ eyes