What are two advantages of data mirroring in a RAID implementation? (Choose two.)

Question

Options

• AIt provides faster random write performance.
• BIt is the least expensive way to implement RAID.
• CIt allows data recovery if a disk failure occurs.
• DIt provides increased capacity.

• A
  91% (21)
• B
  4% (1)
• D
  4% (1)

Explanation

Data mirroring (RAID 1) provides fault tolerance by writing identical data to two or more disks simultaneously, so C is definitively correct - if one drive fails, the mirror copy allows full data recovery without downtime. However, the inclusion of A as correct is actually questionable: standard RAID 1 mirroring does not improve write performance, since every write must go to all mirrored disks; what mirroring can improve is read performance (by reading from whichever disk responds faster). If this question comes from an official exam key, it may contain an error, or it may be referencing RAID 10 (striped mirrors), which does offer write performance gains through striping.

Why the distractors are wrong:

• B (least expensive): RAID 1 requires twice the disks for the same usable storage - it's one of the most expensive RAID types per usable GB.
• D (increased capacity): Mirroring halves your usable capacity; you get redundancy, not extra space.

Memory tip: Think of mirroring as a "safety net, not a speed boost" - its core value is resilience (survive a disk failure), not performance or cost savings. If an exam answer involves mirroring improving write speed, treat it with skepticism; read speed is the performance benefit, not write.

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