Objectives  Describe the physical structure of secondary and tertiary storage devices and the resulting effects on the uses of the devices  Explain the performance characteristics of mass- storage devices  Discuss operating-system services provided for mass storage, including RAID and HSM Operating System Concepts with Java – 8th Edition 12.3 Silberschatz, Galvin and Gagne ©2009
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Objectives  Describe the physical structure of secondary and tertiary storage devices and the resulting effects on the uses of the devices  Explain the performance characteristics of mass-storage devices  Discuss operating-system services provided for mass storage, including RAID and HSM Operating System Concepts Essentials – 8 th Edition 11.3 Silberschatz, Galvin and Gagne ©2011
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RAID Volumes (4 of 4) • When you decide upon using RAID 1 or RAID 5, consider the following: • The boot and system files can be placed on RAID level 1, but not on RAID level 5 • RAID level 1 uses two hard disks and RAID level 5 uses from 3 to 32 • RAID level 1 is more expensive to implement than RAID level 5 • RAID level 5 requires more memory than RAID level 1 • Depending on the disk controller, in Windows Server 2016 disk read access is faster in RAID level 1 and RAID level 5 than is write access © 2018 Cengage. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website for classroom use. 25
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RAID (Cont)  Several improvements in disk-use techniques involve the use of multiple disks working cooperatively  Disk striping uses a group of disks as one storage unit  RAID schemes improve performance and improve the reliability of the storage system by storing redundant data  Mirroring or shadowing (RAID 1) keeps duplicate of each disk  Striped mirrors (RAID 1+0) or mirrored stripes (RAID 0+1) provides high performance and high reliability  Block interleaved parity (RAID 4, 5, 6) uses much less redundancy  RAID within a storage array can still fail if the array fails, so automatic replication of the data between arrays is common Operating System Concepts with Java – 8th Edition 12.21 Silberschatz, Galvin and Gagne ©2009
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RAID (Cont.)  Disk striping uses a group of disks as one storage unit  RAID is arranged into six different levels  RAID schemes improve performance and improve the reliability of the storage system by storing redundant data  Mirroring or shadowing (RAID 1) keeps duplicate of each disk  Striped mirrors (RAID 1+0) or mirrored stripes (RAID 0+1) provides high performance and high reliability  Block interleaved parity (RAID 4, 5, 6) uses much less redundancy  RAID within a storage array can still fail if the array fails, so automatic replication of the data between arrays is common  Frequently, a small number of hot-spare disks are left unallocated, automatically replacing a failed disk and having data rebuilt onto them Operating System Concepts Essentials – 2nd Edition 9.35 Silberschatz, Galvin and Gagne ©2013
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Objectives  To describe the physical structure of secondary storage devices and its effects on the uses of the devices  To explain the performance characteristics of mass-storage devices  To evaluate disk scheduling algorithms  To discuss operating-system services provided for mass storage, including RAID Operating System Concepts Essentials – 2nd Edition 9.3 Silberschatz, Galvin and Gagne ©2013
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RAID (Cont.)  Several improvements in disk-use techniques involve the use of multiple disks working cooperatively  Disk striping uses a group of disks as one storage unit  RAID schemes improve performance and improve the reliability of the storage system by storing redundant data  Mirroring or shadowing (RAID 1) keeps duplicate of each disk  Striped mirrors (RAID 1+0) or mirrored stripes (RAID 0+1) provides high performance and high reliability  Block interleaved parity (RAID 4, 5, 6) uses much less redundancy  RAID within a storage array can still fail if the array fails, so automatic replication of the data between arrays is common  Frequently, a small number of hot-spare disks are left unallocated, automatically replacing a failed disk and having data rebuilt onto them Operating System Concepts Essentials – 8 th Edition 11.33 Silberschatz, Galvin and Gagne ©2011
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Hierarchical Storage Management (HSM)  A hierarchical storage system extends the storage hierarchy beyond primary memory and secondary storage to incorporate tertiary storage — usually implemented as a jukebox of tapes or removable disks.  Usually incorporate tertiary storage by extending the file system   Small and frequently used files remain on disk  Large, old, inactive files are archived to the jukebox HSM is usually found in supercomputing centers and other large installations that have enormous volumes of data. Operating System Concepts Essentials – 8 th Edition 11.49 Silberschatz, Galvin and Gagne ©2011
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C:\UMBC\331\java> java.ext.dirs=C:\JDK1.2\JRE\lib\ext java.io.tmpdir=C:\WINDOWS\TEMP\ os.name=Windows 95 java.vendor=Sun Microsystems Inc. java.awt.printerjob=sun.awt.windows.WPrinterJob java.library.path=C:\JDK1.2\BIN;.;C:\WINDOWS\SYSTEM;C:\... java.vm.specification.vendor=Sun Microsystems Inc. sun.io.unicode.encoding=UnicodeLittle file.encoding=Cp1252 java.specification.vendor=Sun Microsystems Inc. user.language=en user.name=nicholas java.vendor.url.bug=http://java.sun.com/cgi-bin/bugreport... java.vm.name=Classic VM java.class.version=46.0 java.vm.specification.name=Java Virtual Machine Specification sun.boot.library.path=C:\JDK1.2\JRE\bin os.version=4.10 java.vm.version=1.2 java.vm.info=build JDK-1.2-V, native threads, symcjit java.compiler=symcjit path.separator=; file.separator=\ user.dir=C:\UMBC\331\java sun.boot.class.path=C:\JDK1.2\JRE\lib\rt.jar;C:\JDK1.2\JR... user.name=nicholas user.home=C:\WINDOWS C:\UMBC\331\java>java envSnoop -- listing properties -java.specification.name=Java Platform API Specification awt.toolkit=sun.awt.windows.WToolkit java.version=1.2 java.awt.graphicsenv=sun.awt.Win32GraphicsEnvironment user.timezone=America/New_York java.specification.version=1.2 java.vm.vendor=Sun Microsystems Inc. user.home=C:\WINDOWS java.vm.specification.version=1.0 os.arch=x86 java.awt.fonts= java.vendor.url=http://java.sun.com/ user.region=US file.encoding.pkg=sun.io java.home=C:\JDK1.2\JRE java.class.path=C:\Program Files\PhotoDeluxe 2.0\Adob... line.separator=
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Storage Fusion Architecture (SFA) 8 x IB QDR or 16 x FC8 Host Ports Interface Virtualization Interface processor Interface processor Interface Virtualization Interface processor Interface processor Interface processor System memory Interface processor Interface processor Interface processor System memory RAID Processors High-Speed Cache Cache Cache Link Link RAID Processors High-Speed Cache Internal SAS Switching Internal SAS Switching 1 2 3 4 1 2 3 4 1 1mm ©2012 DataDirect Networks. All Rights Reserved. 5 P RAID RAID 5,6 5,6 6 Q RAID RAID 6 6 7 8 P RAID RAID 5,6 5,6 Q RAID RAID 6 6 Up to 1,200 disks in an SFA 10K Or 1,680 disks in an SFA 12K ddn.com
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RAID (Redundant Array of Independent Disks) Technology • There are a number of different disk configurations called RAID levels. – – – – – – – – 11/4/2012 RAID 0 Nonredundant RAID 1 Mirrored RAID 0+1 Nonredundant and Mirrored RAID 2 Memory-Style Error-Correcting Codes RAID 3 Bit-Interleaved Parity RAID 4 Block-Interleaved Parity RAID 5 Block-Interleaved Distributed Parity RAID 6 P+Q Redundancy ISC239 Isabelle Bichindaritz 25
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Types of RAID • RAID 1: Mirroring – Duplicates data on one drive to another drive and is used for fault tolerance (mirrored volume) • RAID 5: uses three or more drives – Stripes data across drives and uses parity checking – Data is not duplicated • RAID 10: RAID 1+0 (pronounced RAID one zero) – Combination of RAID 1 and RAID 0 – Takes at least 4 disks A+ Guide to Managing & Maintaining Your PC, 8th Edition © Cengage Learning 2014 44
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RAID Technology (contd.)  Different raid organizations were defined based on different combinations of the two factors of granularity of data interleaving (striping) and pattern used to compute redundant information.  Raid level 0 has no redundant data and hence has the best write performance at the risk of data loss  Raid level 1 uses mirrored disks.  Raid level 2 uses memory-style redundancy by using Hamming codes, which contain parity bits for distinct overlapping subsets of components. Level 2 includes both error detection and correction.  Raid level 3 uses a single parity disk relying on the disk controller to figure out which disk has failed.  Raid Levels 4 and 5 use block-level data striping, with level 5 distributing data and parity information across all disks.  Raid level 6 applies the so-called P + Q redundancy scheme using Reed-Soloman codes to protect against up to two disk failures by using just two redundant disks. Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 13- 29
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Beginning 1 Developing 2 Accomplished 3 Exemplary 4 Description of identifiable performance characteristics reflecting a beginning level of performance. Description of identifiable performance characteristics reflecting development and movement toward mastery of performance. Description of identifiable performance characteristics reflecting mastery of performance. Description of identifiable performance characteristics reflecting the highest level of performance. Description of identifiable performance characteristics reflecting a beginning level of performance. Description of identifiable performance characteristics reflecting development and movement toward mastery of performance. Description of identifiable performance characteristics reflecting mastery of performance. Description of identifiable performance characteristics reflecting the highest level of performance.   Stated Objective or Performance     Stated Objective or Performance     Score
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Use of RAID Technology (contd.)  Different raid organizations are being used under different situations  Raid level 1 (mirrored disks) is the easiest for rebuild of a disk from other disks   Raid level 2 uses memory-style redundancy by using Hamming codes, which contain parity bits for distinct overlapping subsets of components.    Level 2 includes both error detection and correction. Raid level 3 (single parity disks relying on the disk controller to figure out which disk has failed) and level 5 (block-level data striping) are preferred for Large volume storage, with level 3 giving higher transfer rates. Most popular uses of the RAID technology currently are:   It is used for critical applications like logs Level 0 (with striping), Level 1 (with mirroring) and Level 5 with an extra drive for parity. Design Decisions for RAID include:  Level of RAID, number of disks, choice of parity schemes, and grouping of disks for block-level striping. Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Slide 13- 30
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How to Implement Hardware RAID • Hardware implementation – Hardware RAID controller or RAID controller card • Motherboard does the work, Windows unaware of hardware RAID implementation • Software implementation uses operating system • Best RAID performance – All hard drives in an array should be identical in brand, size, speed, other features • If Windows installed on a RAID hard drive RAID must be implemented before Windows installed A+ Guide to Managing & Maintaining Your PC, 8th Edition © Cengage Learning 2014 45
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RAID Structure  RAID – multiple disk drives provides reliability via redundancy  Increases the mean time to failure  Frequently combined with nonvolatile RAM (NVRAM) to cache the RAID array. This write-back cache is protected from data loss during power failures.  RAID is arranged into six different levels Operating System Concepts with Java – 8th Edition 12.20 Silberschatz, Galvin and Gagne ©2009
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