On Benchmarking Embedded Linux Flash File Systems

Due to its attractive characteristics in terms of performance, weight and power consumption, NAND flash memory became the main non volatile memory (NVM) in embedded systems. Those NVMs also present some specific characteristics/constraints: good but asymmetric I/O performance, limited lifetime, write/erase granularity asymmetry, etc. Those peculiarities are either managed in hardware for flash disks (SSDs, SD cards, USB sticks, etc.) or in software for raw embedded flash chips. When managed in software, flash algorithms and structures are implemented in a specific flash file system (FFS). In this paper, we present a performance study of the most widely used FFSs in embedded Linux: JFFS2, UBIFS,and YAFFS. We show some very particular behaviors and large performance disparities for tested FFS operations such as mounting, copying, and searching file trees, compression, etc.Comment: Embed With Linux, Lorient : France (2012

FFSMark : Un Benchmark pour Systèmes de Fichiers Dédiés aux Mémoires Flash

International audienceLa mémoire flash de type NAND est le principal média de stockage dans l'embarqué. L'un des moyens pour intégrer cette mémoire dans les systèmes informatiques est d'utiliser des systèmes de fichiers dédiés aux mémoires flash (Flash File Systems, FFS). Dans ce domaine, les benchmarks sont des programmes permettant de réaliser des études de performances et de comparer différents systèmes entre eux. Nous montrons dans cet article qu'un benchmark pour FFS doit prendre en compte les caractéristiques spécifiques des mémoires flash, d'une part dans son comportement, et d'autre part en ce qui concerne les métriques de performances disponibles en sortie. Dans ce contexte, nous proposons FFSMark, un benchmark ciblant les FFS, sensible aux spécificités des mémoires flash. FFSMark est dédié à être exécuté sous Linux, un système d'exploitation supportant les FFS les plus populaires. Nous présentons également une étude de cas, utilisant FFSMark pour comparer les performances des FFS JFFS2, YAFFS2 et UBIFS sur une plate-forme embarquée

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

Performance Evaluation of Flash File Systems

Today, flash memory are strongly used in the embedded system domain. NAND flash memories are the building block of main secondary storage systems. Such memories present many benefits in terms of data density, I/O performance, shock resistance and power consumption. Nevertheless, flash does not come without constraints: the write / erase granularity asymmetry and the limited lifetime bring the need for specific management. This can be done through the operating system using dedicated Flash File Systems (FFSs). In this document, we present general concepts about FFSs, and implementations example that are JFFS2, YAFFS2 and UBIFS, the most commonly used flash file systems. Then we give performance evaluation results for these FFSs.Comment: Colloque du GDR SoC-SiP, Paris : France (2012

FIT A Fog Computing Device for Speech TeleTreatments

There is an increasing demand for smart fogcomputing gateways as the size of cloud data is growing. This paper presents a Fog computing interface (FIT) for processing clinical speech data. FIT builds upon our previous work on EchoWear, a wearable technology that validated the use of smartwatches for collecting clinical speech data from patients with Parkinson's disease (PD). The fog interface is a low-power embedded system that acts as a smart interface between the smartwatch and the cloud. It collects, stores, and processes the speech data before sending speech features to secure cloud storage. We developed and validated a working prototype of FIT that enabled remote processing of clinical speech data to get speech clinical features such as loudness, short-time energy, zero-crossing rate, and spectral centroid. We used speech data from six patients with PD in their homes for validating FIT. Our results showed the efficacy of FIT as a Fog interface to translate the clinical speech processing chain (CLIP) from a cloud-based backend to a fog-based smart gateway.Comment: 3 pages, 5 figures, 1 table, 2nd IEEE International Conference on Smart Computing SMARTCOMP 2016, Missouri, USA, 201

I/O Schedulers for Proportionality and Stability on Flash-Based SSDs in Multi-Tenant Environments

The use of flash based Solid State Drives (SSDs) has expanded rapidly into the cloud computing environment. In cloud computing, ensuring the service level objective (SLO) of each server is the major criterion in designing a system. In particular, eliminating performance interference among virtual machines (VMs) on shared storage is a key challenge. However, studies on SSD performance to guarantee SLO in such environments are limited. In this paper, we present analysis of I/O behavior for a shared SSD as storage in terms of proportionality and stability. We show that performance SLOs of SSD based storage systems being shared by VMs or tasks are not satisfactory. We present and analyze the reasons behind the unexpected behavior through examining the components of SSDs such as channels, DRAM buffer, and Native Command Queuing (NCQ). We introduce two novel SSD-aware host level I/O schedulers on Linux, called A & x002B;CFQ and H & x002B;BFQ, based on our analysis and findings. Through experiments on Linux, we analyze I/O proportionality and stability in multi-tenant environments. In addition, through experiments using real workloads, we analyze the performance interference between workloads on a shared SSD. We then show that the proposed I/O schedulers almost eliminate the interference effect seen in CFQ and BFQ, while still providing I/O proportionality and stability for various I/O weighted scenarios

IoT single board computer to replace a home server

Home servers are popular among computer enthusiasts for hosting various applications, including Linux OS with web servers, database solutions, and private cloud services, as well as for VPN, torrent, file-sharing, and streaming. Single Board Computers (SBCs), once used for small projects, have now evolved and can be used to control multiple devices in the IoT space. SBCs have become more powerful and can run many of the same applications as traditional home servers. In light of the energy crisis, this study will examine the feasibility of replacing a conventional home server with an SBC while maintaining service quality and evaluating performance and availability. The power consumption of both solutions will be compared.info:eu-repo/semantics/publishedVersio

CPC: programming with a massive number of lightweight threads

Threads are a convenient and modular abstraction for writing concurrent programs, but often fairly expensive. The standard alternative to threads, event-loop programming, allows much lighter units of concurrency, but leads to code that is difficult to write and even harder to understand. Continuation Passing C (CPC) is a translator that converts a program written in threaded style into a program written with events and native system threads, at the programmer's choice. Together with two undergraduate students, we taught ourselves how to program in CPC by writing Hekate, a massively concurrent network server designed to efficiently handle tens of thousands of simultaneously connected peers. In this paper, we describe a number of programming idioms that we learnt while writing Hekate; while some of these idioms are specific to CPC, many should be applicable to other programming systems with sufficiently cheap threads.Comment: To appear in PLACES'1