RAID Levels & Tradeoffs for A+
Short answer
- RAID 0 (striping): splits data across drives to improve throughput and I/O parallelism but offers no fault tolerance. Use when performance is the only concern and data is not critical. - RAID 1 (mirroring): writes identical data to two drives to provide redundancy; gives fault tolerance for a single drive failure but halves usable capacity. - RAID 5 (striping with parity): uses distributed parity across drives to allow recovery from a single drive failure while providing better usable capacity than mirroring; needs at least three drives and has write-overhead due to parity.
Why it appears on the exam
- Given a requirement emphasizing fault tolerance with minimal drives, choose RAID 1 or RAID 5 and justify. - Given a performance-only requirement with no redundancy, pick RAID 0 and explain the risk. - Given four drives and a need for both performance and redundancy, select RAID 10 and state usable capacity relative to raw capacity.
Key concepts
Concept 1
Required terms
RAID 0: Striping data across multiple drives to increase performance; provides no redundancy. RAID 1: Mirroring data across two drives to provide redundancy; usable capacity equals one drive. RAID 5: Striping with distributed parity across at least three drives to give fault tolerance and better usable capacity than mirroring. RAID 10: A striped set of mirrors (mirroring first, then striping) that provides both redundancy and performance; requires at least four drives.
Example
A video editing scratch RAID where speed is paramount and data is disposable: RAID 0 (temporary workspace only).
Concept 2
How RAID Levels & Tradeoffs works
- RAID 0 (striping): splits data across drives to improve throughput and I/O parallelism but offers no fault tolerance. Use when performance is the only concern and data is not critical. - RAID 1 (mirroring): writes identical data to two drives to provide redundancy; gives fault tolerance for a single drive failure but halves usable capacity. - RAID 5 (striping with parity): uses distributed parity across drives to allow recovery from a single drive failure while providing better usable capacity than mirroring; needs at least three drives and has write-overhead due to parity.
Example
A small database needing quick recovery from drive failure without large capacity loss: RAID 1 for two-drive setups.
Concept 3
Common confusion
Confusing RAID 5 as having no performance cost-parity imposes write overhead. Mixing up RAID 10 and RAID 0+1: while related, RAID 10 requires mirrored pairs that are striped and provides clearer rebuild behavior.
Example
A file server with three to five drives seeking a balance of usable capacity and single-drive fault tolerance: RAID 5.
Concept 4
Core 1 (220-1201) question cues
Given a requirement emphasizing fault tolerance with minimal drives, choose RAID 1 or RAID 5 and justify; Given a performance-only requirement with no redundancy, pick RAID 0 and explain the risk; Given four drives and a need for both performance and redundancy, select RAID 10 and state usable capacity relative to raw capacity.
Example
A system with four or more drives where both redundancy and performance matter (and budget allows): RAID 10.
Sample questions
Select an answer to reveal the explanation. For tracked practice and weak-area review, use the Cultiv8 app.
Q1.An A+ support scenario describes this situation: A video editing scratch RAID where speed is paramount and data is disposable: RAID 0 (temporary workspace only). Which answer fits best?
Q2.A support ticket includes this clue: A small database needing quick recovery from drive failure without large capacity loss: RAID 1 for two-drive setups. Which concept is being tested?
Q3.Read this A+ scenario: A file server with three to five drives seeking a balance of usable capacity and single-drive fault tolerance: RAID 5. Which term or action matches it?
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