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Training Camp • Cybersecurity Glossary
RAID combines multiple physical disks into one logical unit for fault tolerance, speed, or capacity using striping, mirroring, and parity - protecting availability, not backups.
Redundant Array of Independent Disks Definition: RAID combines multiple physical disks into one logical unit for fault tolerance, speed, or capacity using striping, mirroring, and parity - protecting availability, not backups.
Redundant Array of Independent Disks (RAID) is a storage technology that combines multiple physical disk drives into a single logical unit to improve fault tolerance, performance, and capacity. Depending on the configuration, RAID lets a system survive one or more drive failures without data loss and continue operating, supporting the availability pillar of information security.
RAID achieves this through three core techniques, combined into numbered levels. Striping (RAID 0) spreads data across disks for speed but adds no redundancy. Mirroring (RAID 1) writes identical copies to two or more disks so the array survives a drive loss. Parity (RAID 5 and RAID 6) distributes error-correcting parity information across disks, allowing the array to rebuild a failed drive's data - RAID 5 tolerates one failure, RAID 6 tolerates two. Nested levels like RAID 10 combine mirroring and striping for both resilience and performance.
RAID matters because it protects against the most common hardware failure - a dead disk - and keeps services online during a failure and rebuild. Without redundancy, a single drive failure means downtime and potential data loss. A critical caveat for security professionals: RAID is not a backup. It protects against hardware failure, not against ransomware, accidental deletion, file corruption, or site disasters, all of which propagate across the array. RAID supports availability but must be paired with real backups and offsite copies for true data protection.
For example, a database server uses a RAID 6 array of eight disks. When one drive fails, the array keeps serving reads and writes using parity, and the failed disk is hot-swapped while the controller rebuilds it from parity - tolerating even a second failure during the rebuild. However, if ransomware encrypts the database files, RAID faithfully replicates that encryption across all disks, which is why the organization also keeps immutable offsite backups.
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