2 Outline A definition of RAID An ensemble of RAIDs JBOD RAID Configuring and testing a Linux RAID system
3 Motivation Actually, the mass storage devices rely upon mechanical hard drives (HD). Despite the incoming SSDs, the classical HDs remain the preferred solution for computers ranging from notebook to servers. HDs guarantee a huge amount of space with a very small cost/gb. Moreover, modern disks have an improved reliability.
4 Motivation HDs are mechanical devices. A write on a disk requires a disk rotation a correct writing head positioning a stable electrical signal Performance are affected by rpm of the disk, the seek time, the number of plates, the memory buffer, etc. Despite the average life of a modern HD is ~30k hours, they are not a reliable system for data storage and backups.
5 Motivation We need a mass storage device with the following features: Reliable Effective Fast Cheap
6 A definition of RAID Redundant Array of Inexpensive Disks (Patterson, 1988) Redundant Array of Independent Disks (more accepted now). Features Reliable Effective Fast Cheap (not necessarily!!!)
7 A definition of RAID 1. A RAID is a set of standard HDs that are treated as a single logical drive by the OS. 2. A RAID spreads transparently the data on multiple disk. 3. A RAID uses extra storage information to store control codes useful in recovering data after a failure. The standard defines 6 levels of RAID, not a hierarchy, that differ in the implementation of the point 2. and 3.
8 Requirements A RAID requires: A set of disks A controller The controller is the device responsible for reading/writing data on the disks and for consistency check. The controller could be: Software (managed by the OS) Hardware (ad-hoc controller on board, PCI cards, etc).
9 JBOD The JBOD (Just a Bunch of Disks) is not a truly RAID solution. JBOD is usefull for using a set of different disks as a big one. It does not guarantee reliability or performance improvement. Since the disks are linked togheter, when one disk fails the entire JBOD is un-usable.
10 RAID0 A RAID 0 split data across n-disks (n>=2) without any redundancy information. A RAID0 treats data as set ok m-stripes, with each one made of k-sectors. When the OS calls the write routine of the controller, it splits the data into l-stripes and write them on the disks in parallel. Instead, when the OS calls the read routine, the controller makes a parallel reads and it returns the whole data.
12 RAID0 Pros Rapid read operation (if parallel read is supported) Cheap Cons The size of the RAID is equal to the smallest disk size The write and read operations are fast as the slowest disk. No data redundancy
13 RAID 1 RAID1 is the first that assures all the RAID features. In a RAID1, each disk is mirrored. Writing data to the RAID requires a write on each disk. Instead, the data can be read from any disk.
15 RAID 1 Pros Reliable: there is always a copy of each disk. No downtime: simply swap the broken disk Fast read Cons Expensive: for a n-disk RAID1, you need 2n disks. The RAID dimension is equal to the smallest drive of the RAID Total data loss, if two disks are broken.
16 RAID2 Disks are synchronized Very small stripes Often single byte/word Error correction calculated across corresponding bits on disks Multiple parity disks store Hamming code error correction in corresponding positions Lots of redundancy Expensive: log(n) data-disks for parity check Not used
17 RAID0 vs RAID1 vs RAID2
18 RAID 3 Similar to RAID 2, but it works at byte level Only one redundant disk, no matter how large the array Simple parity bit for each set of bits Data on failed drive can be reconstructed from surviving data and parity info Very high transfer rates
19 RAID4 Each disk operates independently A block for each disk One parity disk for any number of data-disk Large stripes Bit by bit parity calculated across stripes on each disk Parity stored on parity disk Good for high I/O request rate
20 RAID 3 vs RAID 4
21 RAID5 Like RAID 4 Parity striped across all disks: each stripe has a parity block. Round robin allocation for parity stripe. Avoids RAID 4 bottleneck at parity disk Commonly used in network servers
Operating Systems RAID Redundant Array of Independent Disks Submitted by Ankur Niyogi 2003EE20367 YOUR DATA IS LOST@#!! Do we have backups of all our data???? - The stuff we cannot afford to lose?? How
200 Chapter 7 (This observation is reinforced and elaborated in Exercises 7.5 and 7.6, and the reader is urged to work through them.) 7.2 RAID Disks are potential bottlenecks for system performance and
SURVEY ON RAID Aishwarya Airen 1, Aarsh Pandit 2, Anshul Sogani 3 1,2,3 A.I.T.R, Indore. Abstract RAID stands for Redundant Array of Independent Disk that is a concept which provides an efficient way for
Fault Tolerance & Reliability CDA 5140 Chapter 3 RAID & Sample Commercial FT Systems - basic concept in these, as with codes, is redundancy to allow system to continue operation even if some components
RAID Basics Training Guide Discover a Higher Level of Performance RAID matters. Rely on Intel RAID. Table of Contents 1. What is RAID? 2. RAID Levels RAID 0 RAID 1 RAID 5 RAID 6 RAID 10 RAID 0+1 RAID 1E
Guest Lecture for 15-440 Disk Array Data Organizations and RAID October 2010, Greg Ganger 1 Plan for today Why have multiple disks? Storage capacity, performance capacity, reliability Load distribution
1/19 Why disk arrays? CPUs speeds increase faster than disks - Time won t really help workloads where disk in bottleneck Some applications (audio/video) require big files Disk arrays - make one logical
Reliability and Fault Tolerance in Storage Dalit Naor/ Dima Sotnikov IBM Haifa Research Storage Systems 1 Advanced Topics on Storage Systems - Spring 2014, Tel-Aviv University http://www.eng.tau.ac.il/semcom
Standard RAID levels From Wikipedia, the free encyclopedia Wikipedia is sustained by people like you. Please donate today. The st andard RAID levels are a basic set of RAID configurations and employ striping,
RAID Technology Overview HP Smart Array RAID Controllers HP Part Number: J6369-90050 Published: September 2007 Edition: 1 Copyright 2007 Hewlett-Packard Development Company L.P. Legal Notices Copyright
Everything you forgot to consider when building your RAID by www.freeraidrecovery.com 2011 RAID is an acronym for Redundant Array of Independent (Inexpensive) Disks. RAID technology allow to combine several
CSE 120 Principles of Operating Systems Fall 2004 Lecture 13: FFS, LFS, RAID Geoffrey M. Voelker Overview We ve looked at disks and file systems generically Now we re going to look at some example file
RAID in a nutshell A Redundant Array of Independent Disks (RAID) is a collection of disks managed by specialized array management software that coordinates their activities. An array s member disks are
Intel RAID Software User s Guide: Intel Embedded Server RAID Technology II Intel Integrated Server RAID Intel RAID Controllers using the Intel RAID Software Stack 3 Revision 8.0 August, 2008 Intel Order
Technology In the 1980s, hard-disk drive capacities were limited and large drives commanded a premium price. As an alternative to costly, high-capacity individual drives, storage system developers began
Checksumming RAID Brian Kroth firstname.lastname@example.org Suli Yang email@example.com Abstract Storage systems exhibit silent data corruptions that go unnoticed until too late, potenially resulting in whole trees
RAID Chunk Size Notices The information in this document is subject to change without notice. While every effort has been made to ensure that all information in this document is accurate, Xyratex accepts
Storage and File Structure Chapter 10: Storage and File Structure Overview of Physical Storage Media Magnetic Disks RAID Tertiary Storage Storage Access File Organization Organization of Records in Files
Flash Media Management Through RAIN Scott Shadley, Senior roduct Marketing Manager Micron Technology, Inc. Technical Marketing Brief What Is RAIN, and Why Do SSDs Need It? This brief compares redundant
Using RAI6 for Advanced ata Protection 2006 Infortrend Corporation. All rights reserved. Table of Contents The Challenge of Fault Tolerance... 3 A Compelling Technology: RAI6... 3 Parity... 4 Why Use RAI6...
Silent data corruption in SATA arrays: A solution Josh Eddy August 2008 Abstract Recent large academic studies have identified the surprising frequency of silent read failures that are not identified or
BrightStor ARCserve Backup for Windows Tape RAID Option Guide r11.5 D01183-1E This documentation and related computer software program (hereinafter referred to as the "Documentation") is for the end user's
IBM ^ xseries ServeRAID Technology Reliability through RAID technology Executive Summary: t long ago, business-critical computing on industry-standard platforms was unheard of. Proprietary systems were
RAID Utility User Guide Instructions for setting up RAID volumes on a computer with a Mac Pro RAID Card or Xserve RAID Card Contents 3 RAID Utility User Guide 3 The RAID Utility Window 4 Running RAID Utility
Best Practices Planning Abstract This white paper provides a set of proven practices for deploying EMC SourceOne Email Management. The information is intended as an enhancement to the information provided
White Paper A New RAID Configuration for Rimage November 2012 Combining RAID 5 and RAID 0 to Reduce the Impact of Hard Drive Failures Rimage is changing the hard drive layout and RAID configurations for
RAID 0 increases with more disks in the array (at a minimum, catastrophic data loss is twice as likely compared to single drives without RAID). A single disk failure destroys the entire array because when