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Systems & Data Center · Intermediate

RAID Rebuild

The process of reconstructing a failed drive's data onto a replacement or spare from mirror copies or parity.

Definition

During a rebuild, the array runs degraded with reduced performance and no (or less) redundancy. Rebuilds on large HDDs can take many hours or days, raising the risk of a second failure.

Example

A 16 TB drive rebuild in RAID 6 takes 30 hours while the array remains online.

Exam tip

Degraded arrays are vulnerable; RAID 6 or RAID 10 reduces rebuild risk compared with RAID 5.

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