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220-1201 Practice Question: A technician is tasked with setting up a RAID 10…
A technician is tasked with setting up a RAID 10 array using four 500 GB HDDs for a database server. After configuration, the total capacity shown is 1 TB instead of the expected 1.5 TB. What is the most likely cause?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The array is configured correctly; RAID 10 provides 1 TB usable.
RAID 10 (1+0) mirrors and then stripes, so usable capacity is half of total raw capacity (4 x 500 GB = 2 TB raw, 1 TB usable). The technician likely expected RAID 5 capacity (75% usable) but configured RAID 10.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
One of the drives is only 250 GB.
Why it's wrong here
If one of the drives were only 250 GB, and the other drives were 500 GB, the usable capacity of the RAID 10 array would be significantly less than 1 TB. RAID 10 is built upon mirrored pairs, and the smallest drive in a pair would limit that pair's capacity. Consequently, the total striped capacity would be reduced, not precisely 1 TB.
- ✗
The array was accidentally configured as RAID 0.
Why it's wrong here
RAID 0, also known as striping, combines the raw capacity of all drives into a single logical volume without any redundancy. With four 500 GB drives, a RAID 0 configuration would yield a total usable capacity of 2 TB (4 x 500 GB), not the 1 TB observed in the scenario.
- ✓
The array is configured correctly; RAID 10 provides 1 TB usable.
Why this is correct
The array is indeed configured correctly for RAID 10 (RAID 1+0). This nested RAID level combines mirroring (RAID 1) for redundancy with striping (RAID 0) for performance. With four 500 GB drives, two mirrored pairs are created, each providing 500 GB of usable space. These two 500 GB logical volumes are then striped together, resulting in a total usable capacity of 1 TB.
- ✗
The controller is using a different stripe size.
Why it's wrong here
Stripe size, or block size, refers to the amount of data written to a single disk in a stripe before moving to the next disk. While an incorrect stripe size can significantly impact the array's read and write performance, it does not affect the total usable storage capacity of the RAID array. The logical capacity is determined by the RAID level and the size of the member drives.
Quick reference
RAID Level Comparison
| RAID Level | Min Disks | Fault Tolerance | Read | Write | Usable Capacity |
|---|---|---|---|---|---|
| RAID 0 | 2 | None | Excellent | Excellent | 100% |
| RAID 1 | 2 | 1 disk | Good | Moderate | 50% |
| RAID 5 | 3 | 1 disk | Good | Moderate | 67–94% |
| RAID 6 | 4 | 2 disks | Good | Lower | 50–88% |
| RAID 10 | 4 | 1 disk per mirror | Excellent | Good | 50% |
RAID is not a backup strategy — it protects against disk failure but not against accidental deletion, ransomware, or site-level events.
Go deeper
Related to this question
Learn chapter
Network Configuration: IP, DNS, DHCP
Key term
RAID
RAID (Redundant Array of Independent Disks) is a data storage technology that combines multiple physical disk drives into one or more logical units for improved performance, fault tolerance, or both.
Key term
RAID 10
RAID 10 combines RAID 1 mirroring and RAID 0 striping to provide both high performance and fault tolerance by writing identical data across mirrored pairs that are then striped for speed.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 220-1201 practice question is part of Courseiva's free CompTIA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 220-1201 exam.