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Chapter 12. Redundant Array of Independent Disks (RAID)

12.1. What is RAID?
12.2. Who Should Use RAID?
12.3. RAID Types
12.4. RAID Levels and Linear Support
12.5. Linux RAID Subsystems
12.6. RAID Support in the Installer
12.7. Configuring RAID Sets
12.8. Advanced RAID Device Creation
The basic idea behind RAID is to combine multiple small, inexpensive disk drives into an array to accomplish performance or redundancy goals not attainable with one large and expensive drive. This array of drives appears to the computer as a single logical storage unit or drive.

12.1. What is RAID?

RAID allows information to be spread across several disks. RAID uses techniques such as disk striping (RAID Level 0), disk mirroring (RAID Level 1), and disk striping with parity (RAID Level 5) to achieve redundancy, lower latency, increased bandwidth, and maximized ability to recover from hard disk crashes.
RAID distributes data across each drive in the array by breaking it down into consistently-sized chunks (commonly 256K or 512k, although other values are acceptable). Each chunk is then written to a hard drive in the RAID array according to the RAID level employed. When the data is read, the process is reversed, giving the illusion that the multiple drives in the array are actually one large drive.