What Is RAID? An Overview of Data Storage Virtualization

RAID (Redundant Array of Independent Disks) is a data storage virtualization technology that combines multiple physical disk drives into one or more logical units to improve data redundancy, performance, or both. Instead of relying on a single disk, RAID distributes data across multiple drives using different schemes known as RAID levels (e.g., RAID 0, RAID 1), each offering a specific balance of reliability, availability, performance, and storage capacity.

RAID achieves its goals through techniques such as:

• Mirroring: Data is duplicated across two or more drives, providing fault tolerance by creating exact copies. This improves read speed but halves effective storage capacity.
• Striping: Data is split across multiple drives to enhance read/write performance, often combined with parity for error detection and correction.
• Parity: A method of error checking that allows data reconstruction in case of drive failure, enhancing fault tolerance without full duplication.

RAID can be implemented in two main forms:

• Hardware RAID: Uses a dedicated RAID controller to manage the disks independently of the host CPU, offering lower latency and better performance but at higher cost and potential single points of failure.
• Software RAID: Managed by the operating system, it is more cost-effective but generally slower due to CPU overhead.

RAID is widely used in environments where data availability and fault tolerance are critical, such as file servers, transaction servers, and application servers. However, it is not always the best choice for virtualization or high-availability failover scenarios.

In summary, RAID is a versatile technology that virtualizes multiple physical drives into logical units to enhance data reliability and/or performance, with various RAID levels tailored to different needs.