Understanding Raid Concepts And Levels; Raid Concepts - 3Ware 9650SE-2LPML User Manual

Chapter 1. Introducing the 3ware® SATA RAID Controller

Understanding RAID Concepts and Levels

RAID Concepts

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For a complete listing of features and system requirements, refer to the 3ware
SATA RAID Controller datasheets, available from the website at
www.3ware.com/products.
3ware RAID controllers use RAID (Redundant Array of Inexpensive Disks)
to increase your storage system's performance and provide fault tolerance
(protection against data loss).
This section organizes information about RAID concepts and configuration
levels into the following topics:
• "RAID Concepts" on page 4
• "Available RAID Configurations" on page 5
• "Determining What RAID Level to Use" on page 11
The following concepts are important to understand when working with a
RAID controller:
• . In the storage industry, the term "array" is used to
Arrays and Units
describe two or more disk drives that appear to the operating system as a
single unit. When working with a 3ware RAID controller, "unit" is the
term used to refer to an array of disks that is configured and managed
through the 3ware software. Single-disk units can also be configured in
the 3ware software.
• . Mirrored arrays (RAID 1) write data to paired drives
Mirroring
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 3ware's TwinStor technology reads from both
drives simultaneously.
• . Striping across disks allows data to be written and accessed on
Striping
more than one drive, at the same time. 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.
• . Parity works in combination with striping on RAID 5,
Distributed Parity
RAID 6, and RAID 50. Parity information is written to each of the striped
3ware Serial ATA RAID Controller User Guide
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