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RAID stands for Redundant Array of Independent Disks. The most commonly used RAID levels are RAID 0, 1, 5, and 6. This is a good article explaining the various RAID levels – PCMag [1]. Below is a short description of each, used as a quick reference.
- RAID 0: Data is striped across multiple disks (requires a minimum of 2 disks). Good for performance because work is done by multiple disks. Provides no data protection.
- RAID 1: Data is mirrored across 2 disks (at minimum). Provides good and simple data protection.
- RAID 2: Data is striped at the bit-level.
- RAID 3: Similar to RAID 5, but requires dedicated parity drive.
- RAID 4: Data is striped at the byte-level.
- RAID 5: Data and parity is striped across multiple disks (requires a minimum of 3 disks). Provides good data protection. If a disk gets an error or starts to fail, data is recreated from this distributed data and parity block [1]. Only one disk can fail without affecting the data. Poor performance on writes.
- RAID 6: Similar to RAID 5, but uses 2 parity blocks. Two disks can fail without affecting the data.