Raid Seminar.Pdf

Total Page:16

File Type:pdf, Size:1020Kb

Raid Seminar.Pdf RAID is an acronym first defined by David A. Patterson, Garth A. Gibson and Randy Katz at the University of California, Berkeley in 1987 to describe a Redundant Array of Inexpensive Disks,[1] a technology that allowed computer users to achieve high levels of storage reliability from low-cost and less reliable PC-class disk- drive components, via the technique of arranging the devices into arrays for redundancy. More recently, marketers representing industry RAID manufacturers reinvented the term to describe a Redundant Array of Independent Disks as a means of disassociating a "low cost" expectation from RAID technology.[2] "RAID" is now used as an umbrella term for computer data storage schemes that can divide and replicate data among multiple hard disk drives. The different schemes/architectures are named by the word RAID followed by a number, as in RAID 0, RAID 1, etc. RAID's various designs all involve two key design goals: increased data reliability or increased input/output performance. When multiple physical disks are set up to use RAID technology, they are said to be in a RAID array. This array distributes data across multiple disks, but the array is seen by the computer user and operating system as one single disk. RAID can be set up to serve several different purposes. Purpose and basics Redundancy is achieved by either writing the same data to multiple drives (known as mirroring), or writing extra data (known as parity data) across the array, calculated such that the failure of one (or possibly more, depending on the type of RAID) disks in the array will not result in loss of data. A failed disk may be replaced by a new one, and the lost data reconstructed from the remaining data and the parity data. Organizing disks into a redundant array decreases the usable storage capacity. For instance, a 2-disk RAID 1 array loses half of the total capacity that would have otherwise been available using both disks independently, and a RAID 5 array with several disks loses the capacity of one disk. Other types of RAID arrays are arranged so that they are faster to write to and read from than a single disk. There are various combinations of these approaches giving different trade-offs of protection against data loss, capacity, and speed. RAID levels 0, 1, and 5 are the most commonly found, and cover most requirements. RAID 0 (striped disks) distributes data across several disks in a way that gives improved speed and no lost capacity, but all data on all disks will be lost if any one disk fails. Although such an array has no actual redundancy, it is customary to call it RAID 0. RAID 1 (mirrored settings/disks) duplicates data across every disk in the array, providing full redundancy. Two (or more) disks each store exactly the same data, at the same time, and at all times. Data is not lost as long as one disk survives. Total capacity of the array equals the capacity of the smallest disk in the array. At any given instant, the contents of each disk in the array are identical to that of every other disk in the array. RAID 5 (striped disks with parity) combines three or more disks in a way that protects data against loss of any one disk; the storage capacity of the array is reduced by one disk. RAID 6 (striped disks with dual parity) (less common) can recover from the loss of two disks. RAID 10 (or 1+0) uses both striping and mirroring. "01" or "0+1" is sometimes distinguished from "10" or "1+0": a striped set of mirrored subsets and a mirrored set of striped subsets are both valid, but distinct, configurations. RAID can involve significant computation when reading and writing information. With traditional "real" RAID hardware, a separate controller does this computation. In other cases the operating system or simpler and less expensive controllers require the host computer's processor to do the computing, which reduces the computer's performance on processor-intensive tasks (see "Software RAID" and "Fake RAID" below). Simpler RAID controllers may provide only levels 0 and 1, which require less processing. RAID systems with redundancy continue working without interruption when one (or possibly more, depending on the type of RAID) disks of the array fail, although they are then vulnerable to further failures. When the bad disk is replaced by a new one the array is rebuilt while the system continues to operate normally. Some systems have to be powered down when removing or adding a drive; others support hot swapping, allowing drives to be replaced without powering down. RAID with hot- swapping is often used in high availability systems, where it is important that the system remains running as much of the time as possible. RAID is not a good alternative to backing up data. Data may become damaged or destroyed without harm to the drive(s) on which they are stored. For example, part of the data may be overwritten by a system malfunction; a file may be damaged or deleted by user error or malice and not noticed for days or weeks; and, of course, the entire array is at risk of physical damage. [edit]Principles RAID combines two or more physical hard disks into a single logical unit by using either special hardware or software. Hardware solutions often are designed to present themselves to the attached system as a single hard drive, so that the operating system would be unaware of the technical workings. For example, you might configure a 1TB RAID 5 array using three 500GB hard drives in hardware RAID, the operating system would simply be presented with a "single" 1TB disk. Software solutions are typically implemented in the operating system and would present the RAID drive as a single drive to applications running upon the operating system. There are three key concepts in RAID: mirroring, the copying of data to more than one disk; striping, the splitting of data across more than one disk; and error correction, where redundant data is stored to allow problems to be detected and possibly fixed (known as fault tolerance). Different RAID levels use one or more of these techniques, depending on the system requirements. RAID's main aim can be either to improve reliability and availability of data, ensuring that important data is available more often than not (e.g. a database of customer orders), or merely to improve the access speed to files (e.g. for a system that delivers video on demand TV programs to many viewers). The configuration affects reliability and performance in different ways. The problem with using more disks is that it is more likely that one will fail, but by using error checking the total system can be made more reliable by being able to survive and repair the failure. Basic mirroring can speed up reading data as a system can read different data from both the disks, but it may be slow for writing if the configuration requires that both disks must confirm that the data is correctly written. Striping is often used for performance, where it allows sequences of data to be read from multiple disks at the same time. Error checking typically will slow the system down as data needs to be read from several places and compared. The design of RAID systems is therefore a compromise and understanding the requirements of a system is important. Modern disk arrays typically provide the facility to select the appropriate RAID configuration. [edit]Standard levels Main article: Standard RAID levels A number of standard schemes have evolved which are referred to as levels. There were five RAID levels originally conceived, but many more variations have evolved, notably several nested levels and many non-standard levels (mostly proprietary). Following is a brief summary of the most commonly used RAID levels.[3] Space efficiency is given as amount of storage space available in an array of n disks, in multiples of the capacity of a single drive. For example if an array holds n=5 drives of 250GB and efficiency is n-1 then available space is 4 times 250GB or roughly 1TB. Level Description Minimum # of disks Space Efficiency Image RAID 0 "Striped set without parity" or "Striping". Provides improved performance and additional storage but no redundancy or fault tolerance. Any disk failure destroys the array, which has greater consequences with more disks in the array (at a minimum, catastrophic data loss is twice as severe compared to single drives without RAID). A single disk failure destroys the entire array because when data is written to a RAID 0 drive, the data is broken into fragments. The number of fragments is dictated by the number of disks in the array. The fragments are written to their respective disks simultaneously on the same sector. This allows smaller sections of the entire chunk of data to be read off the drive in parallel, increasing bandwidth. RAID 0 does not implement error checking so any error is unrecoverable. More disks in the array means higher bandwidth, but greater risk of data loss. 2 n RAID 1 'Mirrored set without parity' or 'Mirroring'. Provides fault tolerance from disk errors and failure of all but one of the drives. Increased read performance occurs when using a multi-threaded operating system that supports split seeks, very small performance reduction when writing. Array continues to operate so long as at least one drive is functioning. Using RAID 1 with a separate controller for each disk is sometimes called duplexing. 2 n/2 RAID 2 Hamming code parity.
Recommended publications
  • Pete's All Things Sun (PATS): the State Of
    We are in the midst of a file sys - tem revolution, and it is called ZFS. File sys- p e t e R B a e R G a Lv i n tem revolutions do not happen very often, so when they do, excitement ensues— Pete’s all things maybe not as much excitement as during a political revolution, but file system revolu- Sun (PATS): the tions are certainly exciting for geeks. What are the signs that we are in a revolution? By state of ZFS my definition, a revolution starts when the Peter Baer Galvin (www.galvin.info) is the Chief peasants (we sysadmins) are unhappy with Technologist for Corporate Technologies, a premier the status quo, some group comes up with systems integrator and VAR (www.cptech.com). Be- fore that, Peter was the systems manager for Brown a better idea, and the idea spreads beyond University’s Computer Science Department. He has written articles and columns for many publications that group and takes on a life of its own. Of and is coauthor of the Operating Systems Concepts course, in a successful revolution the new and Applied Operating Systems Concepts textbooks. As a consultant and trainer, Peter teaches tutorials idea actually takes hold and does improve and gives talks on security and system administra- tion worldwide. the peasant’s lot. [email protected] ;login: has had two previous articles about ZFS. The first, by Tom Haynes, provided an overview of ZFS in the context of building a home file server (;login:, vol. 31, no. 3). In the second, Dawidek and McKusick (;login:, vol.
    [Show full text]
  • The Title Title: Subtitle March 2007
    sub title The Title Title: Subtitle March 2007 Copyright c 2006-2007 BSD Certification Group, Inc. Permission to use, copy, modify, and distribute this documentation for any purpose with or without fee is hereby granted, provided that the above copyright notice and this permission notice appear in all copies. THE DOCUMENTATION IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS DOCUMENTATION INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CON- SEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEG- LIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS DOCUMENTATION. NetBSD and pkgsrc are registered trademarks of the NetBSD Foundation, Inc. FreeBSD is a registered trademark of the FreeBSD Foundation. Contents Introduction vii 1 Installing and Upgrading the OS and Software 1 1.1 Recognize the installation program used by each operating system . 2 1.2 Recognize which commands are available for upgrading the operating system 6 1.3 Understand the difference between a pre-compiled binary and compiling from source . 8 1.4 Understand when it is preferable to install a pre-compiled binary and how to doso ...................................... 9 1.5 Recognize the available methods for compiling a customized binary . 10 1.6 Determine what software is installed on a system . 11 1.7 Determine which software requires upgrading . 12 1.8 Upgrade installed software . 12 1.9 Determine which software have outstanding security advisories .
    [Show full text]
  • Performance and Scalability of a Sensor Data Storage Framework
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Aaltodoc Publication Archive Aalto University School of Science Degree Programme in Computer Science and Engineering Paul Tötterman Performance and Scalability of a Sensor Data Storage Framework Master’s Thesis Helsinki, March 10, 2015 Supervisor: Associate Professor Keijo Heljanko Advisor: Lasse Rasinen M.Sc. (Tech.) Aalto University School of Science ABSTRACT OF Degree Programme in Computer Science and Engineering MASTER’S THESIS Author: Paul Tötterman Title: Performance and Scalability of a Sensor Data Storage Framework Date: March 10, 2015 Pages: 67 Major: Software Technology Code: T-110 Supervisor: Associate Professor Keijo Heljanko Advisor: Lasse Rasinen M.Sc. (Tech.) Modern artificial intelligence and machine learning applications build on analysis and training using large datasets. New research and development does not always start with existing big datasets, but accumulate data over time. The same storage solution does not necessarily cover the scale during the lifetime of the research, especially if scaling up from using common workgroup storage technologies. The storage infrastructure at ZenRobotics has grown using standard workgroup technologies. The current approach is starting to show its limits, while the storage growth is predicted to continue and accelerate. Successful capacity planning and expansion requires a better understanding of the patterns of the use of storage and its growth. We have examined the current storage architecture and stored data from different perspectives in order to gain a better understanding of the situation. By performing a number of experiments we determine key properties of the employed technologies. The combination of these factors allows us to make informed decisions about future storage solutions.
    [Show full text]
  • OS7 User's Manual
    OS7 User’s Manual N2810 Series/ N4810 Series/N5810 Series/ N4910U/N4910U PRO/N4820U N12850 Series/N16850 Series/ N8910/N12910/N12910SAS/N16910SAS Copyright and Trademark Notice Thecus and other names of Thecus products are registered trademarks of Thecus Technology Corp. Microsoft, Windows, and the Windows logo are registered trademarks of Microsoft Corporation. Apple, iTunes and Apple OS X are registered trademarks of Apple Computers, Inc. All other trademarks and brand names are the property of their respective owners. Specifications are subject to change without notice. Copyright © 2017 Thecus Technology Corporation. All rights reserved. About This Manual All information in this manual has been carefully verified to ensure its correctness. In case of an error, please provide us with your feedback. Thecus Technology Corporation reserves the right to modify the contents of this manual without notice. Product name: Thecus OS7.0 used models Manual Version: 1.5.1 Release Date: 2017/06 Limited Warranty Thecus Technology Corporation guarantees all components of Thecus NAS products are thoroughly tested before they leave the factory and should function normally under general usage. In case of any system malfunctions, Thecus Technology Corporation and its local representatives and dealers are responsible for repair without cost to the customer if the product fails within the warranty period and under normal usage. Thecus Technology Corporation is not responsible for any damage or loss of data deemed to be caused by its products. It is highly recommended that users conduct necessary back-up practices. Check the functions that are available on your particular Thecus NAS model at: http://www.Thecus.com 2 Safety Warnings For your safety, please read and follow the following safety warnings: ● Read this manual thoroughly before attempting to set up your Thecus IP storage.
    [Show full text]
  • Computational Scalability of Large Size Image Dissemination
    Computational Scalability of Large Size Image Dissemination Rob Kooper*a, Peter Bajcsya aNational Center for Super Computing Applications University of Illinois, 1205 W. Clark St., Urbana, IL 61801 ABSTRACT We have investigated the computational scalability of image pyramid building needed for dissemination of very large image data. The sources of large images include high resolution microscopes and telescopes, remote sensing and airborne imaging, and high resolution scanners. The term ‘large’ is understood from a user perspective which means either larger than a display size or larger than a memory/disk to hold the image data. The application drivers for our work are digitization projects such as the Lincoln Papers project (each image scan is about 100-150MB or about 5000x8000 pixels with the total number to be around 200,000) and the UIUC library scanning project for historical maps from 17th and 18th century (smaller number but larger images). The goal of our work is understand computational scalability of the web-based dissemination using image pyramids for these large image scans, as well as the preservation aspects of the data. We report our computational benchmarks for (a) building image pyramids to be disseminated using the Microsoft Seadragon library, (b) a computation execution approach using hyper-threading to generate image pyramids and to utilize the underlying hardware, and (c) an image pyramid preservation approach using various hard drive configurations of Redundant Array of Independent Disks (RAID) drives for input/output operations. The benchmarks are obtained with a map (334.61 MB, JPEG format, 17591x15014 pixels). The discussion combines the speed and preservation objectives.
    [Show full text]
  • Of File Systems and Storage Models
    Chapter 4 Of File Systems and Storage Models Disks are always full. It is futile to try to get more disk space. Data expands to fill any void. –Parkinson’sLawasappliedto disks 4.1 Introduction This chapter deals primarily with how we store data. Virtually all computer systems require some way to store data permanently; even so-called “diskless” systems do require access to certain files in order to boot, run and be useful. Albeit stored remotely (or in memory), these bits reside on some sort of storage system. Most frequently, data is stored on local hard disks, but over the last few years more and more of our files have moved “into the cloud”, where di↵erent providers o↵er easy access to large amounts of storage over the network. We have more and more computers depending on access to remote systems, shifting our traditional view of what constitutes a storage device. 74 CHAPTER 4. OF FILE SYSTEMS AND STORAGE MODELS 75 As system administrators, we are responsible for all kinds of devices: we build systems running entirely without local storage just as we maintain the massive enterprise storage arrays that enable decentralized data replication and archival. We manage large numbers of computers with their own hard drives, using a variety of technologies to maximize throughput before the data even gets onto a network. In order to be able to optimize our systems on this level, it is important for us to understand the principal concepts of how data is stored, the di↵erent storage models and disk interfaces.Itisimportanttobeawareofcertain physical properties of our storage media, and the impact they, as well as certain historic limitations, have on how we utilize disks.
    [Show full text]
  • A Secure, Reliable and Performance-Enhancing Storage Architecture Integrating Local and Cloud-Based Storage
    Brigham Young University BYU ScholarsArchive Theses and Dissertations 2016-12-01 A Secure, Reliable and Performance-Enhancing Storage Architecture Integrating Local and Cloud-Based Storage Christopher Glenn Hansen Brigham Young University Follow this and additional works at: https://scholarsarchive.byu.edu/etd Part of the Electrical and Computer Engineering Commons BYU ScholarsArchive Citation Hansen, Christopher Glenn, "A Secure, Reliable and Performance-Enhancing Storage Architecture Integrating Local and Cloud-Based Storage" (2016). Theses and Dissertations. 6470. https://scholarsarchive.byu.edu/etd/6470 This Thesis is brought to you for free and open access by BYU ScholarsArchive. It has been accepted for inclusion in Theses and Dissertations by an authorized administrator of BYU ScholarsArchive. For more information, please contact [email protected], [email protected]. A Secure, Reliable and Performance-Enhancing Storage Architecture Integrating Local and Cloud-Based Storage Christopher Glenn Hansen A thesis submitted to the faculty of Brigham Young University in partial fulfillment of the requirements for the degree of Master of Science James Archibald, Chair Doran Wilde Michael Wirthlin Department of Electrical and Computer Engineering Brigham Young University Copyright © 2016 Christopher Glenn Hansen All Rights Reserved ABSTRACT A Secure, Reliable and Performance-Enhancing Storage Architecture Integrating Local and Cloud-Based Storage Christopher Glenn Hansen Department of Electrical and Computer Engineering, BYU Master of Science The constant evolution of new varieties of computing systems - cloud computing, mobile devices, and Internet of Things, to name a few - have necessitated a growing need for highly reliable, available, secure, and high-performing storage systems. While CPU performance has typically scaled with Moore’s Law, data storage is much less consistent in how quickly perfor- mance increases over time.
    [Show full text]
  • Jupiter® Callisto
    ® OWC Digital Jupiter® Callisto Quick Start Guide TABLE OF CONTENTS 1. INTRODUCTION ..........................................................................................................................................................................1 1.1 CONTENTS 1.2 SPECIFICATIONS (8-BAY) 1.3 SPECIFICATIONS (16-BAY) 1.4 CONNECTIONS AND COMPATIBILITY 1.5 REAR VIEW 1.6 SIDE VIEW 2. ASSEMBLY & REPLACEMENT .................................................................................................................................................4 2.2 UNIT RACK INSTALLATION & REMOVAL 2.2.1 Unit Installation 2.2.2 Unit Removal 2.3 DRIVE INSTALLATION & REMOVAL 2.3.1 Drive Installation 2.3.2 Drive Removal 2.4 POWER SUPPLY FAILURE & REPLACEMENT 2.5 FAN FAILURE 3. INITIAL SETUP ........................................................................................................................................................................... 10 3.1 CONNECTION 3.2 FIRST TIME CONFIGURATION 3.3 ACCESSING THE IPMI INTERFACE 3.4 DEFAULT SETUP 4. STORAGE CONFIGURATION ................................................................................................................................................ 12 4.1 ZFS TERMINOLOGY 4.2 STORAGE CONFIGURATION 4.2.1 Creating the Pool 4.2.2 ZFS RAID Levels 4.2.3 Optimal RAIDZ Configurations 4.2.4 Creating Datasets 4.2.5 Creating a Filesystem 4.2.6 Creating a Zvol 4.3 DRIVE IDENTIFICATION 4.4 DRIVE FAILURE & REPLACEMENT 5. USERS, GROUPS, & PERMISSIONS....................................................................................................................................
    [Show full text]
  • Australian Journal of Basic and Applied Sciences a Review On
    Australian Journal of Basic and Applied Sciences, 9(21) Special 2015, Pages: 86-91 ISSN:1991-8178 Australian Journal of Basic and Applied Sciences Journal home page: www.ajbasweb.com A Review on Raid Levels Implementation and Comparisons P. Sivakumar and K. Devi Department of Computer Science and Engineering Valliammai Engineering College Chennai, Tamilnadu-603203 ARTICLE INFO ABSTRACT Article history: Redundant array of independent disks (RAID) is the technology of grouping several Article Received: 12 January 2015 physical drives in a computer into an array that you can define as one or more logical Revised: 1 May 2015 drives. With RAID technology, data is stripped across an array of physical drives. The Accepted: 8 May 2015 data distribution scheme complements the way for the operating system which requests data. Disk arrays are used to improve performance and reliability. The improvement in Keywords: its quality depends upon the application programs that you run on the server and the RAID, mirroring, stripping, parity, RAID levels that you allocate to the logical drives. Each RAID level provides different RAID manager, Controllers. levels of fault-tolerance (data redundancy), read and write performance and utilization of physical drive capacity. Where ever, the RAID levels differ in view to the minimum and maximum number of physical drives that are supported. We are focused on data redistribution that is necessary to be performed after adding disks to the volume. In this paper we analyze some software's and implement the steps for RAID Technologies and their implementation steps. © 2015 AENSI Publisher All rights reserved. To Cite This Article: P.
    [Show full text]
  • A Primer on Raid Levels: Standard Raid Levels Defined
    A PRIMER ON RAID LEVELS: STANDARD RAID LEVELS DEFINED RAID 0: Disk striping Description: Data is striped across one or more disks in the array. Performance: Since more writers and readers can access bits of data at the same time, performance can be improved. Upside: Performance. Downside: No redundancy. One disk failure will result in lost data. Application(s): Applications that can access data from more sources than just the RAID 0 storage array. RAID 1: Disk mirroring Description: Data is written to two or more disks. No master or primary, the disks are peers. Performance: Read operations are fast since both disks are operational data can be read from both disks at the same time. Write operations, however, are slower because every write operation is done twice. Upside: If one disk fails, the second keeps running with no interruption of data availability. Downside: Cost. Requires twice as much disk space for mirroring. Application(s): Applications that require high performance and high availability including transactional applications, email, and operating systems. RAID 3: Virtual disk blocks Description: Byte-level striping across multiple disks. An additional disk is added that calculates and stores parity information. Performance: Since every write touches multiple disks, every write slows performance. Upside: Data remains fully available if a disk fails. Downside: Performance. Application(s): Good for sequential processing applications such as video imaging. RAID 4: Dedicated parity disk Description: Block-level striping across multiple disks with a cache added to increase read and write performance. Performance: Striping blocks instead of bytes and adding a cache increases performance over RAID 3.
    [Show full text]
  • Raids – Redundant Arrays of Independent Disks More Than Just a Bunch of Disks
    RAIDs { Redundant arrays of independent disks More than just a bunch of disks written by Hauke Stieler, supported by Konstantinos Chasapis Issued on the 13th September, 2015 0UHH-Logo: [Sch] 1 Hauke Stieler RAIDs { Redundant arrays of independent disks Abstract This report is the result of the topic RAID systems in the Proseminar Speicher- und Dateisysteme (stor- age and file systems) of the Department of Informatics at the University of Hamburg during the summer semester 2015. In this paper, you will find an overview of the RAID technology and a list of the most used RAID-levels including combinations of different levels. I will also describe how to set up a RAID in a software or hardware based environment. "A hard drive is like a TARDIS. I like the bit when someone says it's bigger on the inside." { unknown time traveler Picture by [jen]. Last changes made on the 13th September, 2015. For further contact: [email protected] 2 Contents 1 Basics things about RAID 4 1.1 Requirements . 4 1.2 Concepts of RAIDs . 4 1.2.1 Striping . 4 1.2.2 Mirroring . 4 1.2.3 Parity . 4 1.2.4 Hot-Spare . 5 2 RAID Level 5 2.1 Important properties . 5 2.2 Level0............................................... 6 2.3 Level1............................................... 6 2.4 Level2............................................... 6 2.5 Level3............................................... 7 2.6 Level4............................................... 7 2.7 Level5............................................... 7 2.7.1 The XOR operation . 8 2.7.2 Example: Calculate parity . 8 2.7.3 Data recovery . 8 2.8 Level6............................................... 9 2.9 Level 10 & 01 .
    [Show full text]
  • ECE590 Enterprise Storage Architecture Individual Homework #1: Drives and RAID
    ECE590 Enterprise Storage Architecture Individual Homework #1: Drives and RAID Directions: ● This assignment will be completed in INDIVIDUALLY. While you can discuss concepts with others both within and outside your group, actual steps and answers should not be shared! ● The solutions should be collected in a file called ece590-<netid>-hw1.pdf, where <netid> is your Duke NetID (sans brackets!), and submitted via Sakai. Word documents will not be accepted. 1 HDD vs. SSD performance [30pts] 1.1 HDD thought experiment You are optimizing software where the bottleneck is random I/O access to a hard disk drive. You identify two possible improvements: (a) a change to the on-disk data structure so that related data is closer together and often contiguous, or (b) a change so that each record is compressed to a smaller size, but the on-disk layout is otherwise unaffected. Without knowing any additional facts, which do you guess is worth trying first? Why? [5] 1.2 Choosing between HDD and SSD You have a workload that requires 20 TB of capacity and 200,000 IOPS of random I/O performance, mostly reads. You’re going to support it with a storage array, and are deciding between buying Samsung 860 EVO 2TB SSDs or Western Digital Black-series 6TB HDDs. (a) Research the two drives, and identify published benchmarks for IOPS performance (don’t trust manufacturer datasheets). Hint: IOmeter is a common benchmark used for this purpose, and makes a good Google term. You can assume the I/O size is 4kB. Include a link to your sources.
    [Show full text]