IGDTUW 2025 — Computer PYQ

The correct answer is C) To manage multiple hard drives for redundancy and performance.

Conceptual Breakdown

A RAID controller is a hardware or software-based interface that manages one or more hard disk drives (HDDs) or solid-state drives (SSDs) in a computer or storage system. Its primary goals are to ensure data integrity and improve system throughput.

• Redundancy: By mirroring data across multiple disks (RAID 1) or using parity (RAID 5, 6), the controller ensures that if one drive fails, data can be recovered without loss.

• Performance: Through techniques like "striping" (RAID 0), the controller breaks data into smaller chunks and writes them across multiple drives simultaneously, significantly increasing read/write speeds.

Mathematical Representation of RAID Utility

We can represent the reliability and speed gains mathematically. If $R_{disk}$ is the reliability of a single disk, the reliability of a mirrored array $R_{RAID}$ is:

$$R_{RAID}=1-(1-R_{disk}{)}^n$$

Where $n$ is the number of drives. As $n$ increases, the probability of system survival increases drastically compared to a single drive.

Regarding performance, if $T_{single}$ is the time to write data to one disk, the write time for a striped array $T_{RAID}$ across $n$ disks is approximately:

$$T_{RAID}\approx \frac{T_{single}}{n}$$

This demonstrates how a RAID controller optimizes bandwidth by distributing the workload.