Data Availability: RAID

Overview

RAID is an acronym which stands for Redundant Array of Independent Disks. This technology enables you to maintain data redundancy and choose different methods for organizing data on multiple disks. Maintaining redundant data enables you to reconstruct data in the event of a disk failure. Redundant data includes mirrors (duplicate data) and parity information (reconstructing data using an algorithm).

RAID provides different methods for organizing the disk storage. These methods are called RAID levels and are referred to by number, such as RAID 0 or RAID 5. In addition to mirrors and parity information, a RAID level can also use striping, which refers to the process of writing data to equal-sized chunks of disk space across multiple disks. Not all RAID levels provide redundancy. RAID levels can, however, imply an increase or decrease in the system's I/O (read and write) performance. Additionally, maintaining redundant data requires the use of additional disks. As more disks become involved, the chance of a disk failure increases. Because of the differences in I/O performance and redundancy, one RAID level may be more appropriate than another based on the applications in the operating environment and the nature of the data being stored.