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Exercise 3-1 This chapter’s opening scenario illustrates a specific type of incident/disaster. Using a Web browser, search for information related to preparing an organization against terrorist attacks. Look up information on (a) anthrax or another biological attack (like smallpox), (b) sarin or another toxic gas, (c) low-level radiological contamination attacks. Exercise 3-2 Using a Web browser, search for available commercial applications that use various forms of RAID technologies, such as RAID 0 through RAID 5. What is the most common implementation? What is the most expensive?
The following sections discuss the RAID configurations that are most commonly used in the IT industry. RAID Level 0 This is not a form of redundant storage. RAID 0 creates one larger logical volume across several available hard disk drives and stores the data using a process known as disk striping, in which data segments, called stripes, are written in turn to each disk drive in the array. When this is done to allow multiple drives to be combined in order to gain large capacity without data redundancy, it is called disk striping without parity. Unfortunately, failure of one drive may make all data inaccessible. In fact, this level of RAID does not improve the risk situation when using disk drives; instead, it rather increases the risk of losing data from a single drive failure. RAID Level 1 Commonly called disk mirroring, RAID 1 uses twin drives in a computer system. The computer records all data to both drives simultaneously, providing a backup if the primary drive fails. This is a rather expensive and inefficient use of media. A variation of mirroring is called disk duplexing. With mirroring, the same drive controller manages both drives; with disk duplexing, each drive has its own controller. Mirroring is often used to create duplicate copies of operating system volumes for high-availability systems. Using this technique, a plan can be developed that mirrors and then splits disk pairs to create highly available copies of critical system drives. This can make multiple copies of critical data or programs readily available when needed for high-availability computing environments. RAID Level 2 A specialized form of disk striping with parity, RAID 2 is not widely used. It uses a specialized parity coding mechanism known as the Hamming code to store stripes of data on multiple data drives and corresponding redundant error correction on separate error-correcting drives. This approach allows the reconstruction of data if some of the data or redundant parity information is lost. There are no commercial implementations of RAID 2. Failure-Resistant Disk Systems (FRDS) Failure-Tolerant Disk Systems (FTDS) Disaster-Tolerant Disk Systems (DTDS) Protection against data loss due to replaceable unit failure Replaceable unit and environmental failure warning Protection against loss of access to data due to zone failure Replaceable unit monitoring and failure indication Protection against loss of access to data due to device channel failure Long-distance protection against loss of data due to zone failure Protection against loss of access to data due to controller module failure Protection against loss of access to data due to cache failure Protection against loss of access to data due to power supply failure Table 3-3 RAID classification model (continued) © Cengage Learning 2014 Data and Application Resumption 99 Copyright 2013 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. RAID Levels 3 and 4 RAID 3 uses byte-level striping of data, and RAID 4 uses blocklevel striping of data. These approaches use a process in which the data is stored in segments on dedicated data drives, and parity information is stored on a separate drive. Similar to RAID 0, one large volume is used for the data, but the parity drive operates independently to provide error recovery. RAID Level 5 RAID 5 is most commonly used in organizations that balance safety and redundancy against the costs of acquiring and operating the systems. It is similar to RAID 3 and 4 in that it stripes the data across multiple drives, but there is no dedicated parity drive. Instead, segments of data are interleaved with parity data and are written across all the drives in the set. RAID 5 drives can also be hot swapped, meaning they can be replaced without taking the entire system down. RAID Level 6 A combination of RAID 1 and RAID 5, this provides block-level striping with double-distributed parity and allows systems so protected to recover from two simultaneous drive failures. RAID Level 7 This is a proprietary variation on RAID 5 in which the array works as a single virtual drive. RAID 7 is sometimes performed by running special software over RAID 5 hardware. RAID Level 0+1 This is a combination of RAID 0 and RAID 1. Raid 0 is used for its performance, and RAID 1 is used for its fault tolerance. This model creates a second striped set to mirror a primary striped set (striping, then mirroring). RAID Level 1+0 This is a combination of RAID 1 and RAID 0. Raid 0 is used for its performance, and RAID 1 is used for its fault tolerance. This model creates a striped set from a mirrored set (mirroring, then striping). RAID Level 5+1 This is a combination of RAID 5 and RAID 1. Raid 5 is used for its robustness, but then the method adds a separate data parity drive not found in RAID 5
Should be atleast 3 pages
Note: for reference question is from below textbook ,
From Chapter 3, page 123, Real World Exercise 3.1 and 3.2
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