RAID

RAID, Redundant Array of Independent Disks, combines two or more physical drives into a single logical volume that the operating system treats as one disk. It splits or duplicates data across the drives to survive a drive failure, boost read and write speed, or both, depending on the level chosen.

RAID 0 stripes data across drives with no redundancy, so an 8-drive array multiplies capacity and speed but a single failure loses everything. RAID 1 mirrors drives one to one, halving usable capacity. RAID 5 stripes data with one parity block per stripe, tolerating one drive failure while giving up one drive's worth of capacity. RAID 6 adds a second parity block and tolerates two failures. RAID 10 mirrors pairs of drives, then stripes across the mirrors, common in database servers. A dedicated controller card handles parity math in hardware; software RAID does the same work on the host CPU through tools like Linux mdadm or Windows Storage Spaces.

RAID protects against a drive failure, not against accidental deletion, ransomware, or a controller bug that corrupts the whole array, so it never replaces a separate backup. When specing storage, check whether the controller has its own cache and battery backup. Software RAID ties both performance and rebuild times to CPU load.

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Last verified August 29, 2026.