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Systems & Data Center · Foundational

RAID 5

Striping with distributed single parity across three or more drives, tolerating one drive failure.

Definition

Usable capacity is (n-1) drives. Each small write incurs a penalty of four I/Os (read data, read parity, write data, write parity). Long rebuilds on large drives and unrecoverable read errors make RAID 5 risky for high-capacity HDDs.

Example

Five 4 TB drives in RAID 5 yield 16 TB usable.

Exam tip

RAID 5: minimum three drives, capacity n-1, write penalty 4, survives one failure.

Don't confuse it with

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