Secondary Storage Devices Research Articles

Storage Management with Multi-Version Partitioned BTrees

Modern persistent Key/Value-Stores operate on updatable datasets — massively exceeding the size of available main memory. Tree-based key/value storage management structures became particularly popular in storage engines. B+-Trees allow constant search performance, however write-heavy workloads yield inefficient write patterns to secondary storage devices and poor performance characteristics. LSM-Trees overcome this issue by horizontal partitioning fractions of data — small enough to fully reside in main memory, but require frequent maintenance to sustain search performance.To this end, firstly, we propose Multi-Version Partitioned BTrees (MV-PBT) as sole storage and index management structure in key-sorted storage engines like Key/Value-Stores. Secondly, we compare MV-PBT against LSM-Trees. The logical horizontal partitioning in MV-PBT allows leveraging recent advances in modern B+-Tree techniques in a small transparent and memory resident portion of the structure. Structural properties sustain steady read performance, even on historical data, and yield efficient write patterns as well as reduced write-amplification.We integrate MV-PBT in the WiredTiger key/value storage engine. MV-PBT offers an up to 2x increased steady throughput in comparison to LSM-Trees and several orders of magnitude in comparison to B+-Trees in a YCSB workload. Moreover, MV-PBT exhibits robust time-travel query performance and outperforms LSM-Trees by 20% and B+-Trees by an order of magnitude.

Unveiling the electrochemical characteristics of acetonitrile-catholyte-based Na-CO2 battery

The development of metal-CO2 batteries has attracted intense attention because of their unique electrochemical reaction for utilization of CO2 gas. However, unlike the alkali metal-based O2 batteries, a limited number of combinations of aprotic electrolytes have been employed for Li(Na)–CO2 batteries due to the sluggish reaction for the formation of the Li(Na)2CO3 discharge product. Here, we demonstrate an acetonitrile (MeCN)-based catholyte for use in a hybrid cell type Na-CO2 battery. The presence of a solid ceramic separator in our hybrid cell allows the stable operation of the MeCN catholyte-based Na-CO2 battery, resulting in improved electrochemical characteristics such as low overpotential, high energy density, and long cycle stability compared to the conventional TEGDME-based electrolyte. In particular, results of molecular dynamics simulations suggest that the improved performance is mainly due to the enhanced Na+ diffusion in the electrolyte. The calculated barrier for Na+ diffusion in MeCN is approximately four times lower than that in TEGDME. Thus, this work provides a promising electrolyte combination and reveals the mechanism for the improved performance of the MeCN-based electrolyte used in the hybrid cell structure, promoting the development of Na-CO2 batteries as practical secondary energy storage devices.

Assessment of ICT Competencies among Librarians in University Libraries in Bayelsa State, Nigeria

This study reports on the assessment of ICT competencies among librarians in university libraries in Bayelsa State, Nigeria. The reason that necessitated this study was based on the enormous range of tasks which librarians are saddled with in rendering services to users of libraries, thus requiring adequate knowledge and skills to use ICT. A descriptive survey research design was adopted for the study. A population of 72 librarians in four university libraries in Bayelsa State was used for the study. A questionnaire was the instrument for data collection, based on a five-point Likert scale used to measure the ICT competencies of respondents. Data collected were analysed using frequency distribution. Findings from the study revealed that a majority of the librarians had a basic knowledge of ICT competencies such as word processing, storing and copying data from primary and secondary storage devices, retrieving documents from storage devices, electronic presentation, internet surfing, search engines, electronic document delivery, to managing library operations, except in areas of operating systems and software. The study provided insight on how to meet the changing and evolving information needs of users through the incorporation of learning ICT skills/competencies in the digital era. The study recommends the improved implementation of in-house training regarding skills and knowledge in ICT competencies, promoting awareness of ICT competencies in organisational culture, and the acquisition of recent ICT tools, being fundamental for better serving users’ information needs.

Performance analysis of an Injera baking machine by using solar energy

The majority of Ethiopia's population, primarily women, is susceptible to smoke inhalation during cooking, and they spend the majority of their time striving to collect firewood. Biomass deforestation for cooking harms the rural household economy and contributes to national and global environmental change, such as pollution and health issues. The effort should aim to integrate the Scheffler concentrator with a thermal storage system via the secondary solar cooking reflector in order to stimulate indoor cooking while avoiding concerns associated by carbon inhalation and deforestation. As a result, the Injera bakery system powered by solar thermal energy is born. There is a primary (Scheffler), secondary (reflective), and thermal storage device incorporated, as well as a cooking (pan) mounts. Solid works software was utilized for Scheffler focus and secondary reflector modeling and simulation. The thermal retention capacity of a storage device is determined using heating and cooling curves generated by software modeling and simulation. The findings gained would aid in the development of any comfortable indoor cooking system specifically for rural areas without a grid connection, and as a result of this study, carbon inhalation and deforestation difficulties would be mitigated. Through automation, the output rate would also increase the amount and efficiency of injera. This analysis focuses on the Injera baker concept for domestic applications.

Modeling of Battery Management for Standalone PV System

This work is focused on developing a model for a Battery management unit for a Solar PV based off grid standalone system and implementing the same using MATLAB tool. A secondary storage device in form a battery is essential to provide an energy backup in any autonomous system. In this work Lithium ion (Li Ion) battery has been considered for modeling as it offers good charge and discharge profile, high power density, occupies less space and less maintenance. It is essential to ensure secure function of such batteries by closely monitoring and control of their State of Charge (SOC). Determination of SOC ensures the remaining energy available in the battery which further helps in discharging the same based on system requirements. The major components of this work include representation of PV source, employing MPPT, regulating the DC output via boost converter, inverter and controlling the flow of energy between the source to battery, load and vice versa.

An Empirical Evaluation of NVM-Aware File Systems on Intel Optane DC Persistent Memory Modules

The emergence of non-volatile memories (NVM) brings new opportunities and challenges to data management system design. As an important part of the data management systems, several new file systems are developed to take advantage of the characteristics of NVM. However, these NVM-aware file systems are usually designed and evaluated based on simulations or emulations. In order to explore the performance and characteristics of these file systems on real hardware, in this article, we provide an empirical evaluation of NVM-aware file systems on the first commercially available byte-addressable NVM (i.e., the Intel Optane DC Persistent Memory Module (DCPMM)). First, to compare the performance difference between traditional file systems and NVM-aware file systems, we evaluate the performance of Ext4, XFS, F2FS, Ext4-DAX, XFS-DAX, and NOVA file systems on DCPMMs. To compare DCPMMs with other secondary storage devices, we also conduct the same evaluations on Optane SSDs and NAND-flash SSDs. Second, we observe how remote NUMA node access and device mapper striping affect the performance of DCPMMs. Finally, we evaluate the performance of the database (i.e., MySQL) on DCPMMs with Ext4 and Ext4-DAX file systems. We summarize several observations from the evaluation results and performance analysis. We anticipate that these observations will provide implications for various memory and storage systems.

A Comparative Analysis of Disk Scheduling Algorithms

In an operating system, disk scheduling is the process of managing the I/O request to the secondary storage devices such as hard disk. The speed of the processor and primary memory has increased in a rapid way than the secondary storage. Seek time is the important factor in an operating system to get the best access time. For the better performance, speedy servicing of I/O request for secondary memory is very important. The goal of the disk-scheduling algorithm is to minimize the response time and maximize throughput of the system.
 This work analyzed and compared various basic disk scheduling techniques like First Come First Serve (FCFS), Shortest Seek Time First (SSTF), SCAN, LOOK, Circular SCAN (C-SCAN) and Circular LOOK (C-LOOK) along with the corresponding seek time. From the comparative analysis, the result show that C-LOOK algorithm give the least head movement and seek time in different cases as compared to other algorithm. Therefore, it maximizes the throughput for the storage devices.

Construction of sticky ionic conductive buffer layer for inorganic electrolyte toward stable all-solid-state lithium metal batteries

Inorganic electrolyte based all-solid-state lithium metal batteries (LMBs) are considered the most promising secondary power storage device. However, there still exist significant interfacial issues, which hurdles its advancement in application seriously. Herein, we synthesize a sticky anion-immobilized oligomer ionic conductor (AIOC) to construct a buffer layer for inorganic electrolyte. The AIOC displays high ionic conductivity (2.21 × 10−5 S cm−1), large Li+ transference number (0.65) at 30 °C, which is beneficial to promote homogenous lithium deposition, moreover, it endows a wide electrochemical window of 4.3 V (vs. Li+/Li). Based on these merits, when AIOC serves as buffer layer for Li1.5Al0.5Ge1.5(PO4)3 (LAGP) electrolyte, the interfacial stability and compatibility between LAGP and lithium metal anode can be enhanced remarkably. Upon which, the interfacial resistance of lithium symmetrical cell can be declined sharply (5313 Ω→718 Ω). Enduring 100-h galvanostatic charge-discharge cycling test, the surficial morphologies and elemental constitutions of the lithium metal anode and LAGP electrolyte almost remain unchanged as before. As a result, a LiFePO4/Li all-solid-state cell with AIOC modified Li1.5Al0.5Ge1.5(PO4)3 electrolyte enables to achieve a reversible discharge capacity of 120.1 mAh g−1 at 0.5C with a notable capacity retention of 86.3% in 100 cycles at 50 °C.

Optical Disk : Review and Analysis.(Dept.E)

The operating system is a collection of programes (algorithms) designed to manage all the comp uter system resources, such as processors, main storage and secondary storage, and input/output devices. Optical and magnetic disks are the most common secondary storage devices. The work described in this paper is mainly directed to the optical disk. Different optical disk storage technologies are discussed in terms of information about physical disk storage, file systems and access methods. Comparisons are also made between magnetic and optical disk storages.

Single-Atom Iron and Doped Sulfur Improve the Catalysis of Polysulfide Conversion for Obtaining High-Performance Lithium–Sulfur Batteries

Lithium-sulfur (Li-S) batteries are regarded as promising secondary energy storage devices for their high energy density and low cost. The electrochemical performance of Li-S batteries is mainly determined by the efficient and reversible conversion of lithium-polysulfides to Li2S when discharging and to S when charging. Herein, a catalytic strategy is proposed to accelerate the reversible conversion of S and the discharge products in Li-S batteries. This reversible transformation is achieved with active sites of single-atom iron on nitrogen- and sulfur-doped porous carbon (FeNSC). We prove that the synergy between atomically dispersed iron and doped sulfur accelerates the reversible electrochemical conversion reactions in Li-S batteries. The FeNSC/S hybrid cathode exhibits superior long-term cycling stability even at a high current density of 1C, with only 0.047% capacity decay per cycle over 1000 cycles. This study demonstrates a novel method for improving the conversion of polysulfides based on electrocatalysis strategies to ultimately obtain high-performance Li-S batteries.

Temperature-Aware Persistent Data Management for LSM-Tree on 3-D NAND Flash Memory

Key-value (KV) store has been widely deployed in both embedded systems and enterprise systems. Most KV stores today use log structured merge tree (LSM-Tree), as LSM-Tree can eliminate random write operations to the secondary storage and maintain acceptable read performance. LSM-Tree is originally designed for the secondary storage device with hard disk drives. As the emerging storage media, three-dimensional (3-D) flash memory has become the mainstream technology to replace hard disk drives. Different from hard disk drives and the conventional planar flash memory, 3-D flash memory is vulnerable to temperature. High temperature will introduce both charge loss and retention degradation. Since LSM-Tree transfers random write operations to the sequential ones, the access to consecutive physical address in flash memory will cause the temperature issue. This will affect the integrity of data stored in 3-D flash memory. This article presents TLSM, a temperature-aware persistent data management scheme for LSM-Tree-based KV store on 3-D NAND flash memory. TLSM offers both application-level LSM-Tree optimization and firmware-level address management to allocate persistent data to 3-D flash. At the application-level, TLSM presents a novel temperature-aware LSM data structure to reduce the amount of data issued from LSM-Tree to 3-D flash memory. At the firmware-level, TLSM reallocates the data to physical blocks with relatively low temperature. This cross-layer optimization can effectively handle the temperature issue to ensure the data integrity of LSM-Tree in 3-D flash memory. We demonstrate the viability of the proposed scheme using a set of standard benchmarks. Our extensive evaluations show that, TLSM can significantly enhance the data integrity and reduce write amplifications compared to representative schemes.

Determining the Scope of Recovery from Physically Damaged Micro SD Card

Today’s use of secondary devices like cloud storage, Hard Disk, Pen Drive, SD, CDs, DVDs is constantly growing. Data might be deleted , loss or device is formatted accidentally or intentionally by various means. It’s a myth that “once secondary storage devices are damaged then there is no access to data too”. This article gives the detail investigation that from damaged devices too data can be recovered.

A Preliminary Study: Towards Parallel Garbage Collection for NAND Flash-Based SSDs

NAND Flash-based solid-state drives (SSDs) have been widely used as secondary storage devices due to their faster access speed, lower power consumption, and higher reliability compared with hard disk drives. However, application I/O performance can be significantly affected by garbage collection (GC) inside SSDs. For example, a GC operation usually moves valid pages from a victim block into a clean block in a serialized manner. Thus, it increases the GC time and affects the application I/O performance. To address this issue, this article presents a preliminary study on a parallel GC scheme for flash-based SSDs. In our scheme, we parallelize valid page migrations during a GC operation to reduce the total GC time. To do this, we first propose a new flash chip architecture that enables valid page migrations in parallel. Second, we collect information such as new addresses for the migration of valid pages by considering the restriction of SSD operations. Finally, we employ multiple worker threads to migrate the valid pages using the collected information in a parallel manner. We implement and evaluate our scheme using Disksim with Microsoft SSD extension. The experimental result shows that the proposed scheme reduces the overall GC time by 70% and 57% on average compared with the existing scheme and a state-of-the-art GC scheme IPPBE, respectively.

Nanocomposite Gel Polymer Electrolytes: Thermophysical, Electrical Properties and Electrochemical Applications

Flexible polymer-based electrolytes providing good electrode-electrolyte interfaces offer the most promising solution to address the all-solid-state battery requirements.1 However, substantially higher temperatures are required to achieve the optimal conductivity for a polymer electrolyte for electrochemical application, which is still an important bottleneck in lithium polymer batteries. To improve the performance of polymer electrolytes, ionic liquids (ILs) have been combined as a reinforcing agent with suitable polymer matrices. ILs add numerous advantages to the electrolyte such as high thermal stabilities, higher operating temperature range, moderate ion conductivity and safety. Moreover, due to non-reactivity with lithium, IL-based polymer electrolytes may also be used in secondary lithium-metal batteries, outperforming the conventional IL-free polymer electrolytes. In this study, in order to improve the functionality and ion conductivity of polymer electrolyte further, a highly conducting ionic liquid-based nanofluid is used as the plasticizer. The ionanofluid is prepared and optimized by dispersing 5.0wt% of surface functionalized Al2O3 nanoparticles in 1-Decyl-3-methylimidazole bis(trifluoromethanesulfonyl) imide, [Deim][NTf2] IL to achieve the highest conductivity. In order to analyze the thermophysical and electrical properties, the as-prepared lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) salt doped poly (ethylene oxide) based ionanofluid reinforced nanocomposite gel polymer electrolytes are subjected to different characterization techniques viz. XRD, DSC, FT-IR, SEM, HR-TEM and impedance spectroscopy. The highest conductivity for free-standing electrolyte with 30 wt% ionanofluid is obtained as ~2.5×10-3 S/ cm at 30 °C. The electrochemical properties of the optimized highest conducting electrolyte demonstrate its brilliant application potentiality as an electrolyte in secondary energy storage devices.

An Optimized Disk Scheduling Algorithm with Bad-Sector Management

In high performance computing, researchers try to optimize the CPU Scheduling algorithms, for faster and efficient working of computers. But a process needs both CPU bound and I/O bound for completion of its execution. With modernization of computers the speed of processor, hard-disk, and I/O devices increases gradually. Still the data access speed of hard-disk is much less than the speed of the processor. So when processor receives a data from secondary memory it executes immediately and again it have to wait for receiving another data. So the slowness of the hard-disk becomes a bottleneck in the performance of processor. Researchers try to develop and optimize the traditional disk scheduling algorithms for faster data transfer to and from secondary data storage devices. In this paper we try to evolve an optimized scheduling algorithm by reducing the seek time, the rotational latency, and the data transfer time in runtime. This algorithm has the feature to manage the bad-sectors of the hard-disk. It also attempts to reduce power consumption and heat reduction by minimizing bad sector reading time.

OMR: out-of-core MapReduce for large data sets

While single machine MapReduce systems can squeeze out maximum performance from available multi-cores, they are often limited by the size of main memory and can thus only process small datasets. Our experience shows that the state-of-the-art single-machine in-memory MapReduce system Metis frequently experiences out-of-memory crashes. Even though today's computers are equipped with efficient secondary storage devices, the frameworks do not utilize these devices mainly because disk access latencies are much higher than those for main memory. Therefore, the single-machine setup of the Hadoop system performs much slower when it is presented with the datasets which are larger than the main memory. Moreover, such frameworks also require tuning a lot of parameters which puts an added burden on the programmer. In this paper we present OMR, an Out-of-core MapReduce system that not only successfully handles datasets that are far larger than the size of main memory, it also guarantees linear scaling with the growing data sizes. OMR actively minimizes the amount of data to be read/written to/from disk via on-the-fly aggregation and it uses block sequential disk read/write operations whenever disk accesses become necessary to avoid running out of memory. We theoretically prove OMR's linear scalability and empirically demonstrate it by processing datasets that are up to 5x larger than main memory. Our experiments show that in comparison to the standalone single-machine setup of the Hadoop system, OMR delivers far higher performance. Also in contrast to Metis, OMR avoids out-of-memory crashes for large datasets as well as delivers higher performance when datasets are small enough to fit in main memory.

Influence of anion structure on thermal, mechanical, dielectric and electrochemical properties of ZrO2 nanoparticle-pyrrolidinium ionic liquid hybrid electrolytes for the application in energy storage devices

Influence of the two different anion structures viz. bis(fluorosulfonyl)imide (FSI−) and bis(trifluoromethanesulfonyl) imide (TFSI−), on the thermophysical, dielectric and electrochemical properties of ZrO2-nanoparticle tethered pyrrolidinium based nanoscale hybrid ionic fluids (NHIFs) was investigated. Thermal and mechanical properties of NHIFs were found to depend strongly upon the structure of anions and TFSI− comprising NHIF showed better thermal and mechanical stability then its FSI− analogue. Temperature dependent electrical conductivity, dielectric and electrochemical properties of different NHIFs were studied. FSI-NHIF displayed higher ionic conductivity, associated with faster structural relaxation dynamics. At all the measured temperature, FSI-NHIF displayed superior electrochemical cycling performance than its TFSI-equivalent. While, electrochemical cell with TFSI-NHIF showed 81% capacitance retentivity after 5000 charge/discharge cycles, FSI-NHIF cell was found to retain >90% of its initial specific capacitance value after the same. Results obtained from the study optimize the applicability of pyrrolidinium based hybrid ionic fluids as electrolytes in secondary energy storage devices.

Ionic liquid-SnO2 nanoparticle hybrid electrolytes for secondary charge storage devices: Physicochemical and electrochemical studies

A series of nanoscale hybrid ionic fluids (NHIFs) has been prepared by tethering 1-ethyl-3-(3-trimethoxysilylpropyl)-imidazolium bis(trifluoromethanesulfonyl) imide ionic liquids to the surface of SnO2 nanoparticle, at different grafting densities. Investigations reveal that SnO2 nanocores with uniform particle size of 14–17 nm are uniformly dispersed in different NHIF matrices through strong covalent attachment. Thermal stability and mechanical properties of NHIFs are found to improve with increasing grafting density. Temperature dependent electrochemical cycling behaviour of NHIF at different grafting densities are thoroughly investigated. In comparison to pure ionic liquid, the hybrid ionic fluids show substantial enhancement in electrochemical properties, which further improve with increasing grating density. The electrochemical cell containing NHIFs as electrolytes show very good capacitance retentivity (>90%) and long term cyclic stability above room temperature. Results obtained from the study demonstrate the applicability of these hybrid ionic fluids as promising electrolytes in secondary charge storage devices.

Direct Visualization of Li Dendrite Growth Process at Short-Circuit Condition Via Transmission X-Ray Microscopy

Lithium is one of the most favorable materials for next-generation secondary energy storage devices due to its low redox potential, high gravimetric/volumetric capacities, and fast reaction kinetics [1]. However, the use of metallic lithium as the anode has been largely limited by the inherent safety concerns with lithium dendrite growth - causing short-circuits, leading to thermal runaway reactions, and fires/explosions [2]. Many efforts have been devoted to understanding dendrite morphologies with the influencing factors - temperature, electrolyte composition, current density and over-potentials [3]. However, the studies are limited to the nucleation and growth of Li dendrite at early stages [1,2]. At present, the growth mechanism and morphological changes taking place in Li dendrite formation near/after short-circuit condition, which presumably form the basis for its improved performance and safety, are not well understood. Recent advances in in situ electrochemical transmission X-ray microscopy (EC-TXM), with its unique ability to provide simultaneous temporally and spatially resolved information as well as electrochemical parameters, enable exploration of the underlying physics of the electrochemical reactions that occur at the surface and inside of secondary energy storage devices during cycling [4,5]. Here, we focus the direct visualization of the propagation of Li dendrites at short-circuit condition using in situ EC-TXM. After the short-circuit, we follow three-dimensional morphological and microstructural changes of Li dendrites to explore relationships between electrochemical parameters and failure mechanisms during cycling. We further characterize the structural evolution of Li dendrites using in situ X-ray diffraction.

Role of different nanoparticulate cores on the thermal, mechanical and electrochemical cycling behaviour of nanoscale hybrid ionic fluids

Herein, two different nanoscale hybrid ionic fluids (NHIFs) have been demonstrated as potential electrolytes for electrochemical cyclic applications. These NHIFs are prepared by tethering 1-ethyl-3-(3-trimethoxysilylpropyl)-imidazolium bis(trifluoromethanesulfonyl)imide ionic liquids to the surfaces of SiO2 and Al2O3 nanoparticulate cores by simple sol–gel process, resulting in a class of versatile, stable and high-performance gel like materials. Both the NHIFs are mechanically compliant and thermally stable. The NHIFs show wide electrochemical stability window of 8volt that does not shrink with the increase of temperature. Furthermore, the NHIF electrolytic cells containing planar steel electrodes show very good capacitance retentivity (>90%) and long term cyclic stability above room temperature. Relatively higher grafting density of the ionic liquid chains to SiO2 nanoparticles as compared to Al2O3 nanoparticles enables the respective NHIF to show better morphology with superior thermal, mechanical, electrical and electrochemical properties than its Al2O3 tethered analogue. Results obtained from the study highlight the applicability of these hybrid ionic fluids as promising electrolytes in secondary charge storage devices, even at higher temperature.