The document discusses various RAID (Redundant Array of Independent Disks) levels and their implementations in data storage systems, highlighting the differences in redundancy, performance, and cost across RAID 0 to RAID 6. It emphasizes the importance of understanding the strengths and weaknesses of each configuration, including common types like RAID 0 (striping), RAID 1 (mirroring), and RAID 5 (striping with distributed parity). Additionally, it mentions the need for organizations to prepare against potential disasters, such as terrorist attacks, and the relevance of RAID technology in ensuring data resilience.

1. 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

2. 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

3. 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