RAID is a method of storing data by using fault tolerant devices. There are many different RAID techniques, but essentially the concept is to store the same data on multiple hard disks resulting in the redundancy of information. RAID uses a technique known as striping, which involves partitioning each drive’s storage space into units or sectors.

There are at least nine types of RAID plus a non-redundant array (RAID 0):

• RAID 0 - Stripes data across multiple disks, no parity, no redundancy.
• RAID 1 - Disk mirroring, writes data to two identical partitions on separate hard disks creating a full backup. Separate controllers are used.
• RAID 2 - Writes data across multiple disks with error checking.
• RAID 3 - Stripes data one byte at a time and has a dedicated parity drive (for error checking).
• RAID 4 - Stripes data one sector at a time and has a dedicated parity drive (for error checking).
• RAID 5 - Stripes data and parity across multiple disks (at least 3). By mixing the parity across multiple disks a separate parity disk is not required and yet full data redundancy is achieved.

*Note with RAID 5 on an NT box the BOOT and SYSTEM partitions cannot be located on a RAID 5 disk array.

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