We think you have liked this presentation. If you wish to download it, please recommend it to your friends in any social system. Share buttons are a little bit lower. Thank you!
Presentation is loading. Please wait.
Published byCynthia Turner
Modified over 2 years ago
IT 344: Operating Systems Winter 2007 Module 18 Redundant Arrays of Inexpensive Disks (RAID) Chia-Chi Teng CTB 265
6/3/2014 © 2007 Gribble, Lazowska, Levy, Zahorjan 2 The challenge Disk transfer rates are improving, but much less fast than CPU performance We can use multiple disks to improve performance –by striping files across multiple disks (placing parts of each file on a different disk), we can use parallel I/O to improve access time Striping reduces reliability –10 disks have 1/10th the MTBF (mean time between failures) of one disk So, we need striping for performance, but we need something to help with reliability / availability
6/3/2014 © 2007 Gribble, Lazowska, Levy, Zahorjan 3 Reliability Its typically enough to be resilient to a single disk failure –In theory, the odds that another disk fails while youre replacing the first one are low To improve reliability, add redundant data to the disks –Well see how in a moment So: –Performance from striping –Reliability from redundancy (which steals back a bit of the performance gain)
6/3/2014 © 2007 Gribble, Lazowska, Levy, Zahorjan 4 RAID A RAID is a Redundant Array of Inexpensive Disks Disks are small and cheap, so its easy to put lots of disks (10s to 100s) in one box for increased storage, performance, and availability Data plus some redundant information is striped across the disks in some way How striping is done is key to performance and reliability
6/3/2014 © 2007 Gribble, Lazowska, Levy, Zahorjan 5 Some RAID tradeoffs Granularity –fine-grained: stripe each file over all disks high throughput for the file limits transfer to 1 file at a time –course-grained: stripe each file over only a few disks limits throughput for 1 file allows concurrent access to multiple files Redundancy –uniformly distribute redundancy information on disks avoids load-balancing problems –concentrate redundancy information on a small number of disks partition the disks into data disks and redundancy disks
6/3/2014 © 2007 Gribble, Lazowska, Levy, Zahorjan 6 RAID Level 0: Non-Redundant Striping RAID Level 0 is a non-redundant disk array Files are striped across disks, no redundant info High (single file) read throughput Best write throughput (no redundant info to write) Any disk failure results in data loss –What is lost?
6/3/2014 © 2007 Gribble, Lazowska, Levy, Zahorjan 7 RAID Level 1: Mirrored Disks Files are striped across half the disks, and mirrored to the other half –2x space expansion Reads: –Read from either copy Writes: –Write both copies On failure, just use the surviving disk What is the effect on performance? How many simultaneous disk failures can be tolerated?
6/3/2014 © 2007 Gribble, Lazowska, Levy, Zahorjan 8 RAID Levels 2, 3, and 4: Striping + Parity Disk RAID levels 2, 3, and 4 use ECC (error correcting code) or parity disks –E.g., each byte on the parity disk is a parity function of the corresponding bytes on all the other disks A large read accesses all the data disks –A single block read accesses only one disk (RAID 4) A write updates one or more data disks plus the parity disk Resilient to single disk failures (How?) Better ECC higher failure resilience more parity disks
6/3/2014 © 2007 Gribble, Lazowska, Levy, Zahorjan 9 Refresher: Whats parity? To each byte, add a bit set so that the total number of 1s is even Any single missing bit can be reconstructed (Why does memory parity not work quite this way?) Think of ECC as just being similar but fancier (more capable)
6/3/2014 © 2007 Gribble, Lazowska, Levy, Zahorjan 10 RAID Level 5 RAID Level 5 uses block interleaved distributed parity Like parity scheme, but distribute the parity info (as well as data) over all disks –for each block, one disk holds the parity, and the other disks hold the data Significantly better performance –parity disk is not a hot spot...
6/3/2014 © 2007 Gribble, Lazowska, Levy, Zahorjan 11 Typical Implementation Disks Controller OS
6/3/2014 © 2007 Gribble, Lazowska, Levy, Zahorjan 12 RAID 0-1
6/3/2014 © 2007 Gribble, Lazowska, Levy, Zahorjan 13 RAID 5
6/3/2014 © 2007 Gribble, Lazowska, Levy, Zahorjan 14 Final Issues If youre running a RAID level with sufficient redundancy, do you need backup? –Whats the difference between RAID and backup? Does RAID provide sufficient reliability? –If youre Amazon.com? Tier I Single path for power and cooling distribution, no redundant components, % availability. Tier II Single path for power and cooling distribution, redundant components, % availability. Tier III Multiple power and cooling distribution paths, but only one path active, redundant components, concurrently maintainable, % availability. Tier IV Multiple active power and cooling distribution paths, redundant components, fault tolerant, % availability.
CSE 451: Operating Systems Spring 2010 Module 18 Redundant Arrays of Inexpensive Disks (RAID) John Zahorjan Allen Center 534.
CSE 451: Operating Systems Spring 2012 Module 20 Redundant Arrays of Inexpensive Disks (RAID) Ed Lazowska Allen Center 570 ©
Redundant Array of Inexpensive Disks aka Redundant Array of Independent Disks (RAID) Modified from CCT slides.
CSE 451: Operating Systems Winter 2010 Module 13 Redundant Arrays of Inexpensive Disks (RAID) and OS structure Mark Zbikowski Gary Kimura.
RAID Disk Arrays Hank Levy. 212/5/2015 Basic Problems Disks are improving, but much less fast than CPUs We can use multiple disks for improving performance.
I/O Systems and Storage Systems May 22, 2000 Instructor: Gary Kimura.
Chapter 6 RAID. Chapter 6 — Storage and Other I/O Topics — 2 RAID Redundant Array of Inexpensive (Independent) Disks Use multiple smaller disks (c.f.
Other Disk Details. 2 Disk Formatting After manufacturing disk has no information –Is stack of platters coated with magnetizable metal oxide Before use,
RAID Redundant Array of Independent Disks Redundant Array of Inexpensive Disks 6 levels in common use Not a hierarchy Set of physical disks viewed as single.
I/O Errors 1 Computer Organization II © McQuain RAID Redundant Array of Inexpensive (Independent) Disks – Use multiple smaller disks (c.f.
Lecture 36: Chapter 6 Today’s topic –RAID 1. RAID Redundant Array of Inexpensive (Independent) Disks –Use multiple smaller disks (c.f. one large disk)
1 Lecture 18: RAID n I/O bottleneck n JBOD and SLED n striping and mirroring n classic RAID levels: 1 – 5 n additional RAID levels: 6, 0+1, 10 n RAID usage.
RAID (Redundant Arrays of Independent Disks). Disk organization technique that manages a large number of disks, providing a view of a single disk of High.
Servers Redundant Array of Inexpensive Disks (RAID) –A group of hard disks is called a disk array FIGURE Server with redundant NICs.
RAID Redundant Arrays of Inexpensive Disks –Using lots of disk drives improves: Performance Reliability –Alternative: Specialized, high-performance hardware.
RAID Systems CS Introduction to Operating Systems.
RAID- Redundant Array of Inexpensive Drives. Purpose Provide faster data access and larger storage Provide data redundancy.
CSE 321b Computer Organization (2) تنظيم الحاسب (2) 3 rd year, Computer Engineering Winter 2015 Lecture #4 Dr. Hazem Ibrahim Shehata Dept. of Computer.
RAID Oh yes Whats RAID? Redundant Array (of) Independent Disks. A scheme involving multiple disks which replicates data across multiple drives. Methods.
Redundant Array of Independent Disks. Many systems today need to store many terabytes of data. Don’t want to use single, large disk too expensive.
1 RAID Overview n Computing speeds double every 3 years n Disk speeds cant keep up n Data needs higher MTBF than any component in system n IO.
Disk & RAID The first HDD (1956) IBM 305 RAMAC 4 MB 50x24 disks 1200 rpm 100 ms access 35k$/y rent Included computer & accounting software.
Two or more disks Capacity is the same as the total capacity of the drives in the array No fault tolerance-risk of data loss is proportional to the number.
CS 352 : Computer Organization and Design University of Wisconsin-Eau Claire Dan Ernst Storage Systems.
The concept of RAID in Databases By Junaid Ali Siddiqui.
RAID Redundant Array of Independent Disks. 2 Motivation :-)
N-Tier Client/Server Architectures Chapter 4 Server - RAID Copyright 2002, Dr. Ken Hoganson All rights reserved. OS Kernel Concept RAID – Redundant Array.
CS224 Spring 2011 Computer Organization CS224 Chapter 6A: Disk Systems With thanks to M.J. Irwin, D. Patterson, and J. Hennessy for some lecture slide.
CS 346 – April 4 Mass storage –Disk formatting –Managing swap space –RAID Commitment –Please finish chapter 12.
RAID Redundant Arrays of Independent Disks Courtesy of Satya, Fall 99.
RAID SECTION (2.3.5) ASHLEY BAILEY SEYEDFARAZ YASROBI GOKUL SHANKAR.
Redundant Array of Independent Disks (RAID) Striping of data across multiple media for expansion, performance and reliability.
Network-Attached Storage. Network-attached storage devices Attached to a local area network, generally an Ethernet-based network environment.
Lecture 9 of Advanced Databases Storage and File Structure (Part II) Instructor: Mr.Ahmed Al Astal.
Faculty of Information Technology Department of Computer Science Computer Organization Chapter 7 External Memory Mohammad Sharaf.
R.A.I.D. Copyright © 2005 by James Hug Redundant Array of Independent (or Inexpensive) Disks.
CSE 486/586 CSE 486/586 Distributed Systems Case Study: Facebook f4 Steve Ko Computer Sciences and Engineering University at Buffalo.
RAID Redundant Array of Inexpensive Disks Presented by Greg Briggs.
Copyright © Curt Hill, RAID What every server wants!
ICOM 6005 – Database Management Systems Design Dr. Manuel Rodríguez-Martínez Electrical and Computer Engineering Department Lecture 6 – RAID ©Manuel Rodriguez.
RAID: Redundant Array of Inexpensive Disks Supplemental Material not in book.
What is RAID Redundant Array of Independent Disks.
High Performance Computing Course Notes High Performance Storage.
1 Lecture 26: Storage Systems Topics: Storage Systems (Chapter 6), other innovations Final exam stats: Highest: 95 Mean: 70, Median: 73 Toughest.
A CASE FOR REDUNDANT ARRAYS OF INEXPENSIVE DISKS (RAID) D. A. Patterson, G. A. Gibson, R. H. Katz University of California, Berkeley.
I/O – Chapter 8 Introduction Disk Storage and Dependability – 8.2 Buses and other connectors – 8.4 I/O performance measures – 8.6.
© Pearson Education Limited, Chapter 16 Physical Database Design – Step 7 (Monitor and Tune the Operational System) Transparencies.
CSI-09 COMMUNICATION TECHNOLOGY FAULT TOLERANCE AUTHOR: V.V. SUBRAHMANYAM.
RAID and Other Disk Details. 2 Review: Magnetic Disk Characteristic Cylinder: all the tracks under the head at a given point on all surface Read/write.
© 2017 SlidePlayer.com Inc. All rights reserved.