RAID, or Redundant Array of Independent Disks, is a technology that combines multiple physical disk drives into a single logical storage unit to provide improved performance, data availability, and/or data redundancy. There are several different RAID levels, each with its own unique characteristics:
RAID 0 (striping): This level provides improved performance by dividing data evenly across multiple disks, but does not provide any data redundancy. If any disk fails, all data is lost.
RAID 1 (mirroring): This level provides improved data availability by storing copies of data on multiple disks. If one disk fails, the data can still be accessed from the other disks. However, this level provides no improvement in performance.
RAID 5 (striping with parity): This level provides improved performance and data redundancy by storing parity information (used for error correction) across multiple disks. If one disk fails, the data can be reconstructed from the remaining disks and the parity information.
RAID 6 (striping with double parity): This level is similar to RAID 5, but provides additional data redundancy by storing two sets of parity information across multiple disks. If two disks fail, the data can still be reconstructed from the remaining disks and the parity information.
RAID 10 (mirrored striping): This level combines the characteristics of RAID 1 and RAID 0, providing both improved performance and data availability. Data is striped across multiple disks and mirrored onto additional disks.
RAID 50 (striped RAID 5 arrays): This level is similar to RAID 5, but uses multiple RAID 5 arrays that are striped together. It provides improved performance and data redundancy, but requires a minimum of six disks.
These are the most common RAID levels, but there are other variations as well. Linux and Unix systems, as well as Windows Server systems, support a variety of RAID levels and can be configured to use any of the above levels depending on the needs of the system.