RAID

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RAID (Redundant Array of Independent Disks) is a data storage virtualization technology that combines multiple physical disk drive components into one or more logical units for the purposes of data redundancy, performance improvement, or both. RAID is used to improve the performance and reliability of data storage systems.

History

RAID was first defined by David A. Patterson, Garth A. Gibson, and Randy H. Katz at the University of California, Berkeley in 1987. The concept was introduced in a paper titled "A Case for Redundant Arrays of Inexpensive Disks (RAID)," which proposed that a large array of inexpensive disks could outperform the most expensive single disk drives of the time.

RAID Levels

RAID levels refer to the different configurations of RAID, each offering a different balance of performance, redundancy, and storage capacity. The most common RAID levels include:

• RAID 0: Striped set without parity. Provides high performance but no redundancy.
• RAID 1: Mirrored set without parity. Provides redundancy by duplicating data on two disks.
• RAID 5: Striped set with distributed parity. Provides a good balance of performance, redundancy, and storage efficiency.
• RAID 6: Striped set with dual distributed parity. Similar to RAID 5 but with additional redundancy.
• RAID 10: Combination of RAID 1 and RAID 0. Provides high performance and redundancy by mirroring and striping data.

Implementation

RAID can be implemented in two ways: hardware RAID and software RAID.

• Hardware RAID: Uses a dedicated RAID controller to manage the RAID array. This can be a separate card or built into the motherboard.
• Software RAID: Uses the host system's resources to manage the RAID array. This is typically implemented through the operating system.

Advantages and Disadvantages

Advantages

• Performance: RAID can significantly improve read and write speeds, especially in configurations like RAID 0 and RAID 10.
• Redundancy: RAID levels such as RAID 1, RAID 5, and RAID 6 provide data redundancy, protecting against disk failures.
• Scalability: RAID allows for easy expansion of storage capacity by adding more disks to the array.

Disadvantages

• Cost: Implementing RAID, especially hardware RAID, can be expensive due to the need for additional disks and RAID controllers.
• Complexity: Setting up and managing RAID arrays can be complex and may require specialized knowledge.
• Risk of Data Loss: Certain RAID levels, like RAID 0, do not provide redundancy, increasing the risk of data loss.

Applications

RAID is widely used in various applications, including:

• Enterprise Storage: Used in data centers and enterprise environments to ensure data availability and performance.
• Personal Computers: Used by enthusiasts and professionals for improved performance and data protection.
• Servers: Commonly used in servers to provide reliable and fast access to data.

Related Pages

• Disk Storage
• Data Redundancy
• Storage Area Network
• Network Attached Storage
• File System

See Also

• JBOD
• SCSI
• SATA
• NVMe

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