Direct Access Storage Devices Research Articles

KSR-Quadtree: an Intelligent Knowledge Storage and Retrieval Using Quadtree Structure

The size of the data in modern applications grows at an increasing rate. The voluminous database stored in direct access storage device requires more number of disk accesses and the database requires rescanning due to frequent updates. This leads to increased retrieval time. Also, the information retrieved from repository of data cannot guide decision-makers or management to make correct decisions as humans. In this paper, we propose a Knowledge Based System which converts the existing database into Quad tree. Here, the quad trees are used in arriving at decisions on what kind of plants can be that grown in soil based on the domain information (edaphology-soil characteristics) given by the user. The domain information that is stored as an application database is converted into a knowledge base using the dynamic quad-tree data structure. This system is designed with two phases namely, (1) Knowledge storage (as quad-tree) and (2) Effective knowledge retrieval. In the first phase, the records from the database are converted into 2Dpoints and store the point recursively in a two-dimensional space with four recursive quadrants. In the second phase, knowledge retrieval is done with the help of the constructed knowledge base (XML architecture). This system transforms the voluminous database storage into a file thereby reducing the number of disk access and retrieval time. The rescanning of Database is also avoided and supports the edaphologists in making right decisions.

An industrial workstation characterization and selection using quality function deployment

In flexible manufacturing, the need to evaluate various process design concepts that can survive and deliver better performance through many families and generations of products becomes more urgent. It is important to derive characteristics of the assembly station that are measurable and controllable. These characteristics should satisfy process and products needs. In this paper, we report on the findings of a cross-functional team, representing Product Development and Manufacturing Engineering, that was assigned the design of the advanced assembly station required to load magnetic heads suspended by actuator arms in between a stack of media disks in the assembly of direct access storage devices (DASD) also known as hard disk drives (HDD). The core of our work was based on a Quality Function Deployment (QFD) approach that included the construction of a house of quality (John Hauser and Don Clausing, 'The house of quality' Technical Report, Operations Department, Harvard Business School, Boston, MA 02163; Bob King, 'Better Designs in Half the Time, Implementing Quality Function Deployment in America, 3rd edn, Goal/QPC Publishing, MA, 1989) which treated this process step as a system. We present results of the team efforts and describe the progressive stages that took place from the gathering of the station customers' wants and needs to the selection of a station design.

Mechatronics in storage technology

Storage technology is an essential part of computing. The most common device currently in use to store data is the direct access storage device (DASD) or disk drives as they are commonly known. Since their inception in 1956, DASD's have undergone a revolutionary change, and now several generations later store, retrieve, and archive massive quantities of data reliably at a rate (data rate) that renders real-time computing, graphical display, and other forms of data processing possible. The demand for data storage continues to increase very rapidly and therefore, the designers of disk drives continue to push the limits and find new frontiers in recording. At the same time, new methods of recording to increase the data densities and data rate are being pursued. Phase change optical recording and magneto-optical recording show promise for data storage for multimedia applications on one hand and inexpensive storage and retrieval devices such as magnetic tape drives are in wide use for common storage needs where data rate is of little significance. In designing of these devices, expertise in many disciplines such as electromagnetics, mechanics, tribology, heat and mass transfer, mechanical design and dynamics of mechanisms is required and the design process is very complicated. In this article, we will study how these disciplines come together and are linked together. Thus Mechatronics in the disk drives applications means study of interactive effects of disciplines listed above.

Architectural verification of advanced storage controllers

The architectural complexity of advanced storage controllers has increased to a point at which architectural verification methods based on document inspections and reviews are no longer effective. To facilitate the architectural verification process, a high-performance simulator (TurboSim) has been developed for architectural-level verification. The TurboSim application includes a set of architectural-level models, which represent essential architectural components, and an automatic test case generator (ATG). The TurboSim ATG is used to generate realistic representations of customer direct access storage device (DASD) track data. The track data are used to drive different TurboSim simulation scenarios. After demonstrating its effectiveness as an architectural verification tool, TurboSim was enhanced to support the automatic generation of hardware test cases. These hardware test cases are used to ensure that the hardware implementation matches architectural specifications.

Redundant Array of Inexpensive Disks (RAID): Technology Description, Characterizations, Comparisons, Usage and Cost Benefits

Customer requirements have guided the evolution and implementation of software and hardware computer data storage technologies. The concept of RAID originated with a group of researchers at the University of California at Berkeley (UCB). They were investigating the use of an array of small capacity, inexpensive personal computer direct access storage devices (DASD) managed by a special type of a controller, as an alternative to the single large expensive disk (SLED) subsystems more common on mainframe computers. The disk arrays can be configured differently to provide different levels of operational capabilities, each providing special advantages in reliability and data availability, speed and economy. Different configurations are referred to as different levels of RAID. Berkeley originally defined a basic set of RAID levels ranging from RAID, level 0 (RAID 0) through RAID, level 5 (RAID 5). The RAID technology vendors have since extended the RAID level domain by defining RAID 6 and beyond to accommodate additional functionality. Each RAID type has shown itself to be suitable for certain applications. The projected reduction in storage costs and facilities, $/GB and ft2/GB respectively, using the present RAID technology and its projected evolution are phenomenal.

Interaction of Focused Radiation with Magneto-optical Discs

Abstract Direct access storage devices are widely used in computers to store and manage data. In conventional magnetic recording, a magnetic head flying very close to the disc surface alters the polarization of the magnetic field at the disc surface to write and/or erase information on the disc. An optical disc is a multilayered medium consisting of a thick glass substrate on which many layers of different materials are sputtered. Only one of these layers serves as a recording medium and it is initially magnetized uniformly in one direction. To write on this disc, the initial magnetic field is altered by focusing light from a laser source with high numerical aperture (NA) lens to heat the magnetic medium beyond its Curie point, the temperature at which the magnetic medium loses its magnetization. This domain with zero magnetization is subsequently magnetized in the reversed direction by using an induction magnet. All these processes take place while the disc is rotating at a very high speed with respect t...

Automated optical mass storage system with 3-beam magneto-optical disk drives

An automated optical mass storage system (optical MSS) with high-speed magnetooptical (MO) disk drives has been developed. It features a high data transfer rate for writing with the use of the 130-mm ISO standard MO disk, and disk cartridges with high storage efficiency. As the key device, a high-speed MO disk drive has been developed. It provides a high-speed data writing capability of about ten times that of conventional MO disk drives. The optical MSS provides a data transfer rate for reading and writing of 2.1 MB/s, a storage capacity of 250 GB to 1 TB, and an average cartridge handling time of 5 s. From performance simulations, the optical MSS is proved to be applicable to a low-traffic random-access file that stores multimedia data and a high-speed direct-access storage device (DASD) backup file.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Grouped sweeping scheduling for DASD-based multimedia storage management

This paper presents a new formulation of DASD (direct access storage device) disk arm scheduling schemes for multimedia storage management. The formulation, referred to as grouped sweeping scheduling (GSS), provides a framework for minimizing the buffer space required in the retrieval of multimedia streams. In GSS, the set ofn media streams that are to be served concurrently is divided intog groups. Groups are served in fixed order and streams within each group are served in an elevator-like SCAN scheme. Hence, the fixed order (FIFO) and SCAN schemes are special cases of GSS wheng=n andg=1, respectively. In this paper an optimization problem is formulated in which the buffer requirement is minimized with respect to the two design parameters:g and the size of the service unit, i.e. the number of blocks accessed in each service cycle. This formulation initially assumes that all media streams have the same playout requirements. A procedure of complexityO(1) is developed in computing the optimum solution to this problem. The proof of optimality and comparisons between the optimized GSS scheme and FIFO and SCAN are also presented. The paper also discusses the effect of disk arrays in the GSS formulation and issues related to operating GSS in a dynamic setting where streams arrive and depart in random order. Finally, the GSS scheme is extended to support heterogeneous media streams where each stream may have its own playout requirement.

Laser-Induced Heating of a Multilayered Medium Resting on a Half-Space: Part II—Moving Source

Direct access storage devices (DASDs) are widely used in the computer industry to store and manage data. In conventional magnetic recording, an induction head flying very close to the disk surface alters the polarization of the magnetic field of the disk surface to erase and/or write the information on the disk. However, a new technology known as magneto-optical recording or optical recording has considerable promise to increase data densities and reliability of data storage. In magneto-optical storage, magnetic fields are altered by a laser source, which heats the magnetic medium beyond its Curie point, a temperature at which the magnetic medium loses its magnetization. This domain with zero magnetization is subsequently reversed by using an induction magnet. All these processes take place when the disk is rotating at a very high speed with respect to the laser source. An optical disk is a multilayered medium consisting of a thick glass disk on which many layers of different materials are sputtered, only one layer of which serves as a magnetic medium. Therefore, in this paper, a problem of laser-induced heating of a multilayered medium resting on a half-space is considered when the laser is translating with respect to it. The transient heat conduction equation is solved by employing the Laplace transform in the time domain and the Fourier Transform in the x, y dimensions. The resulting ordinary differential equation is solved and the inversion of the Laplace transform is obtained by a technique developed by Crump. The Fourier inversion is obtained by using a Fast Fourier Transform. The technique developed here is then applied to calculate domain size for recorded bits for a given disk, laser power, source characteristics, and rotational velocity.

FEMvis: An interactive visualization tool for mechanical analysis

Increasing competitiveness in the development and manufacturing of mechanically based products requires ever-increasing design and development cycles, and has stimulated the introduction of many computer-based tools to assist with mechanical design and analysis. Currently, strong emphasis is placed upon the effectiveness of such tools, and on their enhancement through improved usability. A major contribution to improved usability is the level of interactiveness of a tool. FEMvis is a tool that provides capabilities for interactive visualization of mechanical engineering analysis, including rotation, translation, and magnification of images; views of shape deformations, their time-evolution, and their superposition; visualizations of scalar fields in two and three dimensions using colored isolevels; blending of shape deformation images and isolevel images; visualizations of three-dimensional phenomena by moving a slicing plane through the image, showing cross-sectional deformations and isolevels; and visualizations of multiple shape deformations and multiple scalar fields during a single usage session. FEMvis has been implemented in a portable language and a portable graphics package, and can run on a spectrum of hardware platforms from workstations to mainframes. It has been applied to the mechanical analysis of direct-access storage devices (DASD), including stress, strain, modal, and deformation analyses. The interactive nature of FEMvis facilitates iterative design refinement and rapid prototyping.

Materials Challenges in Integrated Optical Recording Heads

Integrated optical recording head concepts show promise for future light-weight and compact optical heads. Several fundamental issues remain to be explored before fully integrated optical heads. become a reality. This article reviews the basic operating principles of integrated optic heads, focusing on the materials challenges inherent in developing both partially and fully integrated optical heads.Currently available optical mass storage systems provide a feature unavailable in magnetic direct access storage devices (DASD) — removable and interchangeable media. At present, however, this feature is bought at a price, with magnetic storage devices currently outperforming their optical counterparts in access speed and volumetric storage density. The access time of optical drives is greater than 40 ms, compared to the 10–20 ms typical of magnetic DASD. This is, in large part, a consequence of the 50–100 g moving mass of the optical head. The optical head also limits the maximum volumetric storage density, with current heads ranging from about 0.5 cm to more than 2 cm in height.

Advanced particulate media for high density DASD

Barium ferrite and Co- gamma Fe/sub 2/O/sub 3/ particles comprise the leading particulate media for high-density direct-access storage devices (DASD). The physical, chemical, and magnetic properties of barium ferrite and Co- gamma Fe/sub 2/O/sub 3/ particles and media having film thicknesses of 0.25 mu m are compared. Magnetic and recording properties of isotropic and longitudinally oriented barium ferrite, Co- gamma Fe/sub 2/O/sub 3/, and mixtures thereof confirm its potential for high-density DASD. Linear densities (-3 dB) exceeding 1400 fc/mm were achieved without equalization. Barium ferrite media show both particulate and metal-films noise behavior. >

The Analysis of a Self-Acting Flexible Foil Slider Bearing

The flexible foil slider bearing is an alternate approach to the design of low clearance slider bearings used in direct access storage devices. The flexible foil, or membrane design will be presented as a slider bearing with high film stiffness that can achieve competitive flying heights. The elastohydrodynamics of the membrane slider design will be examined. A steady-state analysis will examine the effects on membrane shape of various physical parameters such as membrane stiffness, and membrane surface backing pressure. A transient analysis will assess the fluid film stiffness of the membrane slider. The membrane slider design has impressive compatibility between the slider and the disk surface for single impulse disturbances as well as continuous or ripple disturbances.

Models of DASD Subsystems with Multiple Access Paths: A Throughput-Driven Approach

A throughput-driven approach to the performance analysis of direct access storage devices (DASD's), i.e., disks, is presented for a model of a block-multiplexor channel system with multiple transfer paths. The approach relies on a step-wise analysis of shared components within the data transfer path: head of string, control unit, channel, referred to as blocking points. In order to derive the service time of an I/O request, each blocking point is analyzed separately, using essentially a classical loss-system model. The advantages of the method are its relative simplicity and applicability to a large number of configurations. Transient and boundary effects, including the miss probability on second and subsequent reconnection attempts, and the device reconnection window (lead time), are also discussed. The inclusion of the approach in a larger system model, as well as its relationship with previous work on DASD analysis is considered. Numerical results illustrate the accuracy of the method.

Models of DASD subsystems: Basic model of reconnection

In this paper, devoted to modeling the performance of Direct Access Storage Devices (DASDs), a basic model of a block-multiplexor channel is developed. The goal is to properly and simply represent the missed reconnection effect together with its influence on the overall performance of a DASD subsystem. The approach taken is that of step-wise decomposition and analysis under loads of constant numbers of users. Computational algorithms for evaluating the solution obtained are considered. The use of the basic model as a building block for more complex systems is illustrated in the example of a symmetrical two-CPU system with shared disks. Finally, the limitations of the approach are discussed.

Models of DASD subsystems: Basic model of reconnection

In this paper, devoted to modeling the performance of Direct Access Storage Devices (DASDs), a basic model of a block-multiplexor channel is developed. The goal is to properly and simply represent the missed reconnection effect together with its influence on the overall performance of a DASD subsystem. The approach taken is that of step-wise decomposition and analysis under loads of constant numbers of users. Computational algorithms for evaluating the solution obtained are considered. The use of the basic model as a building block for more complex systems is illustrated in the example of a symmetrical two-CPU system with shared disks. Finally, the limitations of the approach are discussed.

Database Machines: An Introduction

THIS issue of the IEEE TRANSACTIONS ON COMPUTERS iS devoted to the relatively new field of database machine design. What is a database machine? This question is answered in the context of the traditional approach to the storage, retrieval, and update of information. A collection of data is called a file, and the file is composed of individual records. The records themselves are partitioned into fields. In punched card technology, a file is a deck of cards, a record is a single card (a unit record), and a field is a grouping of adjacent columns to which the designer has assigned some meaning. Simple data processing systems access files in a sequential manner, processing each record in turn. This technique is well suited to the relatively inexpensive card and tape storage media. In the more expensive direct access (drum and disk) storage technologies, the storage media is divided into tracks. Tracks can be addressed directly, which leads to the concept of constructing an index of the file which indicates what data are stored on each track. With direct access storage devices and suitable file organization techniques, data processing programs can search, update, insert, and delete records from a file without processing the entire file in a sequential fashion. Direct access storage devices provide the user with more powerful functions, but these functions must be programmed on the central processor, as the IO interface traditionally communicates control information at a very low level.

Optimal storage allocation for serial files

A computer system uses several serial files. The files reside on a direct-access storage device in which storage space is limited. Records are added to the files either by jobs in batch processing mode, or by on-line transactions. Each transaction (or job) generates a demand vector which designates the space required in each file for record addition. Whenever one file runs out of space, the system must be reorganized. This paper considers several criteria for best allocating storage space to the files.

A note on estimating hit ratios for direct-access storage devices

A note on estimating hit ratios for direct-access storage devices

The algorithm sequential access method

A requirement of many computer file processing systems is the ability to access data stored on a direct access storage device (DASD) both sequentially and randomly. A popular method which provides both types of access is the index sequential organization. The purpose of this study is to propose and analyze a file organization method which should be appropriate for the same type of environment as index sequential but would be more efficient at the two types of access. This proposed method is designated the Algorithm Sequential Access Method (ASAM).