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.)  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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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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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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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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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 (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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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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Software RAID vs. Hardware RAID • Software RAID implements fault tolerance through the server’s operating system • Hardware RAID is implemented through the server hardware • Independent of the operating system • Advantages of hardware RAID over software RAID: • Faster read and write response • The ability to place boot and system files on different RAID levels • The ability to ‘‘hot-swap’’ a failed disk • More setup options to retrieve damaged data © 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. 31
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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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Chapter 2: Operating-System Structures  Operating System Services  User Operating System Interface  System Calls  Types of System Calls  System Programs  Operating System Design and Implementation  Operating System Structure  Virtual Machines  Operating System Debugging  Operating System Generation  System Boot Operating System Concepts – 8th Edition 2.2 Silberschatz, Galvin and Gagne ©2009
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Chapter 2: Operating-System Structures  Operating System Services  User Operating System Interface  System Calls  Types of System Calls  System Programs  Operating System Design and Implementation  Operating System Structure  Virtual Machines  Operating System Debugging  Operating System Generation  System Boot Operating System Concepts – 8th Edition 2.2 Silberschatz, Galvin and Gagne ©2009
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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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RAID Volumes (1 of 4) • RAID is a set of standards for lengthening disk life, preventing data loss, and enabling relatively uninterrupted access to data • Windows Server 2016 supports RAID levels 0, 1, and 5 • RAID level 0 • Striping with no other redundancy features (such as no parity or mirroring) • RAID level 0 is not recommended in many situations because it does not really provide fault tolerance • RAID level 1 • Disk duplexing is the same as disk mirroring, with the exception that it places the backup disk on a different controller or adapter than is used by the main disk • RAID level 5 • Combines the best features of RAID, including striping, error correction, and checksum verification © 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. 22
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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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Simple levels of RAID • RAID 0 – Striping • RAID 1 – Mirrored Volumes • RAID 2 – Bit-level striping with parity distributed to one or more disks • RAID 3 – Byte-level striping with dedicated parity disk • RAID 4 – Block-level striping with dedicated parity disk • RAID 5 – Block-level striping with distributed parity • RAID 6 – Block-level striping with distributed double parity
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Chapter 2: Operating-System Structures  Operating System Services  User Operating System Interface  System Calls  Types of System Calls  System Programs  Operating System Design and Implementation  Operating System Structure  Virtual Machines  Operating System Debugging  Operating System Generation  System Boot Operating System Concepts Essentials – 8th Edition 2.2 Silberschatz, Galvin and Gagne ©2011
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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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Essential RAID levels RAID level 0 (striping)  RAID level 1 (mirroring and duplexing)  RAID level 2  RAID level 3  RAID level 4  RAID level 5 (striping combined with error correction and checksum verification)  Guide to Operating System Security 28
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Nested RAID • RAID 0+1: striped sets in a mirrored set • RAID 10 (or RAID 1+0): mirrored sets in a striped set • RAID 5+1: mirrored striped set with distributed parity (also known as RAID 53) • RAID 5+0: striped set of RAID-5 sets
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RAID Support in Windows 2000 Server/Server 2003 (Continued)  Configuration considerations    Boot and system files can be placed on RAID level 1, but not on RAID level 5 RAID level 1 uses two hard disks; RAID level 5 uses from 3 to 32 RAID level 1 is more expensive to implement than RAID level 5 Guide to Operating System Security 30
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Software RAID versus Hardware RAID  Software RAID   Implements fault tolerance through computer’s operating system Hardware RAID    Implemented through RAID hardware (eg, adapter) Independent of operating system More expensive than software RAID Guide to Operating System Security 36
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