External-memory Dictionaries in the Affine and PDAM Models

2021 ◽  
Vol 8 (3) ◽  
pp. 1-20
Author(s):  
Michael A. Bender ◽  
Alex Conway ◽  
Martín Farach-Colton ◽  
William Jannen ◽  
Yizheng Jiao ◽  
...  
Keyword(s):  
Unit Cost ◽  
Ease Of Use ◽  
Hard Drives ◽  
Transfer Data ◽  
Storage Devices ◽  
Affine Model ◽  
B Trees ◽  
Internal Operations ◽  
Disk Access ◽  
Node Size

Storage devices have complex performance profiles, including costs to initiate IOs (e.g., seek times in hard drives), parallelism and bank conflicts (in SSDs), costs to transfer data, and firmware-internal operations. The Disk-access Machine (DAM) model simplifies reality by assuming that storage devices transfer data in blocks of size B and that all transfers have unit cost. Despite its simplifications, the DAM model is reasonably accurate. In fact, if B is set to the half-bandwidth point, where the latency and bandwidth of the hardware are equal, then the DAM approximates the IO cost on any hardware to within a factor of 2. Furthermore, the DAM model explains the popularity of B-trees in the 1970s and the current popularity of B ɛ -trees and log-structured merge trees. But it fails to explain why some B-trees use small nodes, whereas all B ɛ -trees use large nodes. In a DAM, all IOs, and hence all nodes, are the same size. In this article, we show that the affine and PDAM models, which are small refinements of the DAM model, yield a surprisingly large improvement in predictability without sacrificing ease of use. We present benchmarks on a large collection of storage devices showing that the affine and PDAM models give good approximations of the performance characteristics of hard drives and SSDs, respectively. We show that the affine model explains node-size choices in B-trees and B ɛ -trees. Furthermore, the models predict that B-trees are highly sensitive to variations in the node size, whereas B ɛ -trees are much less sensitive. These predictions are born out empirically. Finally, we show that in both the affine and PDAM models, it pays to organize data structures to exploit varying IO size. In the affine model, B ɛ -trees can be optimized so that all operations are simultaneously optimal, even up to lower-order terms. In the PDAM model, B ɛ -trees (or B-trees) can be organized so that both sequential and concurrent workloads are handled efficiently. We conclude that the DAM model is useful as a first cut when designing or analyzing an algorithm or data structure but the affine and PDAM models enable the algorithm designer to optimize parameter choices and fill in design details.

scholarly journals Performance of Movable Head Disk Storage Devices with Various Disk Scheduling Algorithms

2019 ◽  
Vol 9 (2S) ◽  
pp. 486-490
Keyword(s):  
Scheduling Algorithms ◽  
Access Time ◽  
Processing Unit ◽  
Disk Scheduling ◽  
Efficient Manner ◽  
Hard Drives ◽  
Storage Devices ◽  
Disk Storage ◽  
Central Processing ◽  
The One

Hard drives are the one which needs to be accessed in an efficient manner so that it is feasible to get better recital of the central processing unit. Now a day’s magnetic disks are capable of providing more input output bandwidth yet a huge amount of this bandwidth is lost due to the access time of the hard disk. This paper discusses an analysis of performance of various disk scheduling algorithms with their merits and demerits

Effect of node size on the performance of cache-conscious B + -trees

2003 ◽  
Vol 31 (1) ◽  
pp. 283-294 ◽  
Author(s):  
Richard A. Hankins ◽  
Jignesh M. Patel
Keyword(s):  
B Trees ◽  
Node Size

scholarly journals Evaluating Encryption Algorithms for Sensitive Data Using Different Storage Devices

2020 ◽  
Vol 2020 ◽  
pp. 1-9 ◽  
Author(s):  
Bahman A. Sassani (Sarrafpour) ◽  
Mohammed Alkorbi ◽  
Noreen Jamil ◽  
M. Asif Naeem ◽  
Farhaan Mirza
Keyword(s):  
Flash Memory ◽  
Full Range ◽  
Data Encryption ◽  
Storage Device ◽  
Sensitive Data ◽  
Hard Drives ◽  
Storage Devices ◽  
Aes Algorithm ◽  
Encryption Algorithms ◽  
Storage Encryption

Sensitive data need to be protected from being stolen and read by unauthorized persons regardless of whether the data are stored in hard drives, flash memory, laptops, desktops, and other storage devices. In an enterprise environment where sensitive data is stored on storage devices, such as financial or military data, encryption is used in the storage device to ensure data confidentiality. Nowadays, the SSD-based NAND storage devices are favored over HDD and SSHD to store data because they offer increased performance and reduced access latency to the client. In this paper, the performance of different symmetric encryption algorithms is evaluated on HDD, SSHD, and SSD-based NAND MLC flash memory using two different storage encryption software. Based on the experiments we carried out, Advanced Encryption Standard (AES) algorithm on HDD outperforms Serpent and Twofish algorithms in terms of random read speed and write speed (both sequentially and randomly), whereas Twofish algorithm is slightly faster than AES in sequential reading on SSHD and SSD-based NAND MLC flash memory. By conducting full range of evaluative tests across HDD, SSHD, and SSD, our experimental results can give better idea for the storage consumers to determine which kind of storage device and encryption algorithm is suitable for their purposes. This will give them an opportunity to continuously achieve the best performance of the storage device and secure their sensitive data.

Reallocated Sectors Count Parameter for Analysing Hard Disk Drive Reliability

2019 ◽  
Vol 16 (12) ◽  
pp. 5298-5302
Author(s):  
Iskandar Nailovich Nasyrov ◽  
Ildar Iskandarovich Nasyrov ◽  
Rustam Iskandarovich Nasyrov ◽  
Bulat Askarovich Khairullin
Keyword(s):  
Operating Time ◽  
Disk Drive ◽  
Disk Surface ◽  
Information Storage ◽  
Hard Drives ◽  
Storage Devices ◽  
Reliability Parameters ◽  
Individual Assessment ◽  
Scientific Task ◽  
Rate Frequency

The dependence of the SMART parameter 5 Reallocated sectors count value change on the operating time characterising the number of reallocated sectors is considered. This parameter is critical in the sense that if the attribute value increases, this may indicate deterioration in the state of the disk surface. The scientific task of the study is to establish relationships in the failed hard drives between the specified parameter and the values of other reliability parameters for information stores of various manufacturers. In the course of the study, the drives of the HGST, Hitachi, Samsung, ST, Toshiba, WDC trademarks operated in the Backblaze largest commercial data centre were analysed. The analysis revealed a relationship between the specified parameter and the parameters 1 Read error rate (frequency of errors (when reading data from the disk), the origin of which is due to the hardware of the disk), 196 Reallocation event count (number of reallocation operations), 197 Current pending sector count (number of sectors that are candidates for reallocation). It is shown that the nature of the change in the values of the considered parameters depends on the manufacturer of information storage devices. It is proposed to perform an individual assessment of the reliability of hard drives using the parameters identified as a result of the study.

scholarly journals Economics of maize grain storage at household level in Chuadanga district of Bangladesh

2017 ◽  
Vol 42 (3) ◽  
pp. 549-561
Author(s):  
ME Baksh ◽  
F Rossi ◽  
MA Momin ◽  
P Hajong ◽  
TP Tiwari
Keyword(s):  
Service Providers ◽  
Storage Systems ◽  
Storage System ◽  
Unit Cost ◽  
Grain Storage ◽  
Storage Devices ◽  
Household Level ◽  
Plastic Bags ◽  
Maize Grain ◽  
Bengali Language

There is a common perception among farmers and concerned professionals that maize grain cannot be stored like paddy or other cereals in conventional rural storage devices. As such, farmers generally sell their produce at harvest for any price offered to avoid quality deterioration and losing total return after harvest, which leads to lower profitability. To counter this situation, in the recent years, some progressive farmers at Chuadanga district (one of the concentrated maize growing area of Bangladesh) have been storing their maize grain within their household by using traditional bamboo granaries (Golas in the Bengali language) with the aim to capture higher future prices, while these Golas are traditionally used for storing paddy. Through the Cereal Systems Initiative for South Asia in Bangladesh (CSISA-BD) project, the International Maize and Wheat Improvement Center (CIMMYT) also helps further more to disseminate this technologies in the Chuadanga area. Given the uptake of this profitincreasing strategy by farmers, it is essential to document and evaluate the knowledge learned in order to inform scale-out efforts designed to reach farmers in other areas. A survey was conducted to assess maize grain storage systems in use at the household level in Chuadanga District farmers, and to estimate the overall profitability of storing maize grain. The survey results showed that approximately 80% of the total maize grain produced in 2014 (5.93 t/ha, on average) by sampled farmers was stored; most households employed Gola (62%) and/or jute sacks (55%), among other options. Golas were their first preference, followed by storage systems that pair polythene bags with (respectively) jute sacks and plastic bags, and then several other options. On average, farmers stored their maize grain 25.6 weeks (2014), 21 weeks (2013), and 20.9 weeks (2012) while realizing a price benefit of BDT 2.16/kg, BDT 4.72/kg, and BDT 5.35/kg in the respective years. Despite the fact that average storage costs and average quantities stored both varied by less than 7% between 2012 and 2014, the profit per unit (100 kg) and profit per household was significantly less in 2014 (BDT 10,161) than in 2013(BDT 24,445) and 2012 (BDT 30,255), due to the much lower price differential obtained from maize grain storage in 2014. Examination of the total unit cost of storage reveals that the Golas were the most profitable storage system employed by the farmers and its profits helps farmers to improve their livelihood. Proper dissemination of these practices (storing and Gola) could be helpful for the farmers at the intensive maize growing area. Limitation of drying space and higher labour cost were the two major problems faced by the farmers, introducing quick-drying devices (flatbed dryers) can solve both the problems. It can be established either by local service providers, or farmers organizing themselves for collective ownership of such equipment.Bangladesh J. Agril. Res. 42(3): 549-561, September 2017

scholarly journals A review of hand-held Electrocardiogram (ECG) recording devices

2021 ◽  
Vol 20 (Supplement_1) ◽  
Author(s):  
MC Collins ◽  
EE Elliott ◽  
NS Stain ◽  
JM Malcolmson ◽  
CM Monkhouse
Keyword(s):  
Data Transfer ◽  
Low Cost ◽  
False Positive Rate ◽  
Unit Cost ◽  
Pilot Trial ◽  
Cost Effective ◽  
Visual Assessment ◽  
Ease Of Use ◽  
Exclusion Criteria ◽  
Electrocardiogram Ecg

Abstract Funding Acknowledgements Type of funding sources: Public hospital(s). Main funding source(s): St Barts NHS Trust Introduction The advent of portable hand-held devices to record an electrocardiogram (ECG) in-clinic, has the potential to streamline patient assessment in many clinical environments. These ECG technologies are able to record one to six lead ECGs and enable rapid responses to clinical situations. These devices may also have a role in reducing interdepartmental movement of patients during the COVID-19 pandemic, by facilitating a one-stop shop for clinical evaluation.  However despite their benefit, they can be more prone to artefact than a 12-lead ECG. Purpose To describe the currently available hand-held ECG technologies, their ease of use and diagnostic accuracy for rhythm assessment. Method An online review was conducted to identify new ECG technologies. Clinical colleagues were also surveyed for recommendations with respect to specifications, availability of alternative products, and informed of the inclusion /exclusion criteria. The review included devices which had built-in abnormal rhythm notification or display, were cost-effective and easy to use. Devices were automatically excluded if cutaneous skin electrodes were required, no in-built ECG display or notification, additional data transfer required to access ECG data or a high unit cost. Results An initial search uncovered nine devices, with five meeting inclusion /exclusion criteria. These devices were tabulated and compared predefined criteria (See table 1: ECG Technology comparisons). The analysis revealed that all devices utilised two finger placement on their recording electrodes to produce immediate ECG results – no cutaneous ECG application required. The KardiaMobile 6L™ had the largest number of beneficial features, namely multi-channel device, QTc interpretation, rapid diagnosis time and low cost. The intended use of hand-held devices is to detect AF. Four of five devices produced a snapshot ECG for rhythm identification on their display. However, AfibAlert™ devices provided an instant light alert if atrial fibrillation (AF) was detected. Instant check™, Dimitek™ and AfibAlert™ benefit from being complete stand-alone devices. In contrast, KardioMobile devices have a built-in ECG display for instant review however, they require a smart phone or tablet to store and transfer the data. These devices support a reliable internal AF algorithm to obtain a high negative predicted value to safely rule out AF. Frequent premature atrial contractions (PACs) are often difficult to distinguish from AF and can lead to high false-positive rate. Hand-held devices are prone to artefact, however accurate visual assessment able to significantly reduce the amount of ECGs deemed uninterpretable. Conclusions Hand-held ECG technology has potential to become a useful, cost-effective tool during patient consultations, with rapid identification of clinically important arrhythmias. However, limitations exist across providers. A pilot trial of these devices is planned to assess further.

scholarly journals Performance of Cryptographic Hash function used in Digital Forensic tools

2021 ◽  
Keyword(s):  
Hash Functions ◽  
Hash Tables ◽  
Cyber Forensics ◽  
Hard Drives ◽  
Storage Devices ◽  
Digital Forensic ◽  
Length Data ◽  
Forensic Tools ◽  
Evaluation Of Evidence ◽  
Image Archives

Cryptographic hash functions are which transform any long message to fixed-length data. It seeks to ensure the confidentiality of the data through the cryptographic hash. The digital forensic tool is a method for extracting information from various storage devices, such as hard drives, memory. SHA-1 and SHA-2 methods are both widely used in forensic image archives. The hash method is usually used during evidence processing, the checking of forensic images (duplicate evidence), then at the completion of the analysis again to ensure data integrity and forensic evaluation of evidence. There was a vulnerability called a collision in the hashing algorithm in which two independent messages had the same hash values. While SHA-3 is secure than its former counterparts, the processors for general purposes are being slow and are not yet so popular. This task proposes a basic yet successful framework to meet the needs of cyber forensics, combining hash functions with other cryptographic concepts, for instance, SALT, such as modified secured hash algorithm (MSHA). A salt applies to the hashing mechanism to make it exclusive, expand its complexity and reduce user attacks like hash tables without increasing user requirements.

scholarly journals REVIEW AND JUSTIFICATION OF THE ENERGY STORAGE DEVICES SELECTION FOR ELECTRIC POWER FACILITIES OPERATION

2020 ◽  
pp. 198-209
Author(s):  
Dmytro Zakharchenko ◽  
◽  
Serhii Stepenko ◽  
Keyword(s):  
Energy Storage ◽  
Environmental Impact ◽  
Service Life ◽  
Unit Cost ◽  
Electric Energy ◽  
Optimal Choice ◽  
Energy Storage Devices ◽  
Electricity Storage ◽  
Storage Devices ◽  
Advantages And Disadvantages

Urgency of the research.The study of electricity storage for the operation of power facilities, characteristics and their consideration when choosing the type of storage for the facility will optimize the system as a whole.Target setting.Scientific and technical development and the environmental situation make more stringent requirements for the power system.Actual scientific researches and issues analysis.The classification and main characteristics of existing energy storage devices, their main advantages and disadvantages are considered.Uninvestigated parts of general matters defining. ThereThe main problem with the use of new types of electricity storage is the lack of their widespread use in the market of electricity facilities.The research objective.The aim of the work is to develop a methodology for determining the optimal type and model of universal electricity storage and analysis of its advantages and disadvantages.The statement of basic materials. The analysis of existing types of electric energy storage devices and their characteristics is carried out. Methods are proposed that are based on a comparison of unit cost, volume capacity, environmental impact and service life. The main differences of each type of electricity storage, their advantages and disadvantages are analyzed.Conclusions.The proposed method is based on a comparison of unit cost, volume capacity, environmental impact and service life. The main differences of each type of electricity storage, their advantages and disadvantages are analyzed. Using the proposed technique, the optimal choice of electricity storage for power facilities is made.

scholarly journals A Novel B-Tree Index with Cascade Memory Nodes for Improving Sequential Write Performance on Flash Storage Devices

2020 ◽  
Vol 10 (3) ◽  
pp. 747
Author(s):  
Bo-Kyeong Kim ◽  
Gun-Woo Kim ◽  
Dong-Ho Lee
Keyword(s):  
Flash Memory ◽  
High Reliability ◽  
Index Structure ◽  
Storage Device ◽  
Nand Flash ◽  
Solid State Drives ◽  
Flash Storage ◽  
Storage Devices ◽  
B Trees ◽  
Tree Index

Flash storage devices such as solid-state drives and multimedia cards have been widely used in various applications because of their fast access speed, low power consumption, and high reliability. They consist of NAND flash memories that perform slow block erasures before overwriting data on a prewritten page. This characteristic can lead to performance degradation when applying the original B-tree on the flash storage device without any changes. Although various B-trees have been proposed for flash memory, they still require many flash operations that degrade overall performance. To address the problem, we propose a novel B-tree index structure that reduces the number of write operations and improves the sequential writes by employing cascade memory nodes. The proposed B-tree index structure delays the updates for the modified B-tree nodes and later performs batch writes in a cascade manner. Also, when records with continuous key values are sequentially inserted, the proposed B-tree index structure does not split the leaf node so that it improves write throughput and page utilization. Through mathematical analysis and experimental results, we show that the proposed B-tree index structure always yields better performance than existing techniques.

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