Incorrect Statements on Disk Mirroring

B.

With mirroring, the system writes the data simultaneously to separate drives or arrays.

The advantage of mirroring are minimal downtime, simple data recovery, and increased performance in reading from the disk.

The disadvantage of mirroring is that both drives or disk arrays are processing in the writing to disks function, which can hinder system performance.

Mirroring has a high fault tolerance and can be implemented either through a hardware RAID controller or through the operating system.

Since it requires twice the disk space than actual data, mirroring is the less cost-efficient data redundancy strategy.

Source: SWANSON, Marianne, & al., National Institute of Standards and Technology (NIST), NIST Special Publication 800-34, Contingency Planning Guide for Information Technology Systems, December 2001 (page 45).

Disk mirroring is a technique in which data is stored simultaneously on two or more hard drives to provide data redundancy and fault tolerance. In the event of a disk failure, the data can be recovered from the remaining disk(s). Here are the explanations of each statement and their correctness:

A. Mirroring offers better performance in read operations but writing hinders system performance. This statement is generally true. Since data is written to both disks simultaneously, write operations may take longer, reducing system performance. However, read operations can be faster because the data can be read from either disk.

B. Mirroring is a hardware-based solution only. This statement is false. Disk mirroring can be implemented either in hardware or software. In hardware-based mirroring, the mirroring is performed by the disk controller or a specialized RAID card. In software-based mirroring, the mirroring is performed by the operating system.

C. Mirroring offers a higher fault tolerance than parity. This statement is generally true. Disk mirroring provides a higher level of fault tolerance than parity because it duplicates data onto two or more disks. In contrast, parity-based systems use parity information to reconstruct data in the event of a disk failure, which is less reliable than having a complete copy of the data on another disk.

D. Mirroring is usually the less cost-effective solution. This statement is generally true. Disk mirroring is a more expensive solution than parity because it requires at least two disks to mirror data. In contrast, parity-based systems can provide fault tolerance with only one additional disk for storing parity information.

Therefore, the incorrect statement regarding disk mirroring is B. Mirroring can be implemented in hardware or software.