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RAID Concepts
The following concepts are important to understand when working with a RAID controller:

| Arrays and Units. In the storage industry, an array refers to two or more disk drives that appear to the operating system as a single unit. When working with a RAID controller, unit refers to an array of disks that you can configured and manage through the 3ware software. You can also use the 3ware software to configure Single-disk units.

| Mirroring. Mirrored arrays (RAID 1) write data to paired drives simultaneously. If one drive fails, the data is preserved on the paired drive. Mirroring provides data protection through redundancy. In addition, mirroring using a 3ware RAID controller provides improved performance because the 3ware TwinStor® technology reads from both drives simultaneously.

| Striping. Striping across disks allows data to be written and accessed on more than one drive simultaneously. Striping combines each drive’s capacity into one large volume. Striped disk arrays (RAID 0) achieve highest transfer rates and performance at the expense of fault tolerance.

| Distributed Parity. Parity works in combination with striping on RAID 5, RAID 6, and RAID 50. Parity information is written to each of the striped drives, in rotation. If a failure occurs, you can reconstructed the data on the failed drive from the data on the other drives.

| Hot Swap. The process of exchanging a drive without shutting down the system. This process is useful when you need to exchange a defective drive in a redundant unit.

| Array Roaming. The process of from a controller and putting it back either on the same controller, or a different controller, and having the unit recognized as a unit. You can attach the disks to different ports without harm to the data.

Related Topics
  Available RAID Configurations
  Determining Which RAID Level to Use
  Getting Started with Your 3ware RAID Controller
  Configuring Units

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