Which of the following RAID levels is not used in practice and was quickly superseded by the more flexible
levels?

A.
RAID Level 0

B.
RAID Level 1

C.
RAID Level 2

D.
RAID Level 7

Explanation:
RAID Level 2 consists of bit-interleaved data on multiple disks. The parity information is created using a
hamming code that detects errors and establishes which part of which drive is in error. It defines a disk drive
system with 39 disks: 32 disks of user storage 66 and seven disks of error recovery coding. This level is not
used in practice and was quickly superseded by the more flexible levels.
Incorrect Answers:
A: RAID Level 0 “Writes files in stripes across multiple disks without the use of parity information. This
technique allows for fast reading and writing to disk. However, without the parity information, it is not possible to
recover from a hard drive failure. This technique does not provide redundancy and should not be used for
systems with high availability requirements. RAID Level 0 is widely used today where performance is required
but not redundancy.
B: RAID Level 1 “This level duplicates all disk writes from one disk to another to create two identical drives. This
technique is also known as data mirroring. RAID Level 1 is widely used today.
D: RAID Level 7 is a variation of RAID 5 wherein the array functions as a single virtual disk in the hardware.
This is sometimes simulated by software running over a RAID level 5 hardware implementation. This enables
the drive array to continue to operate if any disk or any path to any disk fails. RAID Level 7 was not superseded
by the more flexible levels.

Krutz, Ronald L. and Russel Dean Vines, The CISSP Prep Guide: Mastering the Ten Domains of Computer
Security, John Wiley & Sons, New York, 2003, p. 90