hardMultiple ChoiceObjective-mapped
220-1201 Practice Question: A technician is troubleshooting a server that…
A technician is troubleshooting a server that uses a RAID 5 array with three 2 TB HDDs. The array reports 4 TB of usable space. One drive fails. What is the immediate impact on data availability?
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 continues to function, but performance may decrease until the drive is replaced.
RAID 5 can tolerate one drive failure without data loss because parity data is distributed across all drives. The array will continue to operate in a degraded state until the failed drive is replaced and rebuilt. A second failure would cause data loss.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
All data is lost because RAID 5 cannot handle any drive failures.
Why it's wrong here
This statement is incorrect. RAID 5 utilizes distributed parity across all drives in the array, specifically designed to provide fault tolerance against a single drive failure. When one drive fails, the data from the lost drive can be reconstructed using the parity information and the data from the remaining operational drives, preventing data loss.
- ✓
The array continues to function, but performance may decrease until the drive is replaced.
Why this is correct
This is the correct behavior for a RAID 5 array experiencing a single drive failure. The array enters a degraded state, where it remains operational and data is still accessible, but it must actively reconstruct missing data on-the-fly using parity calculations. This real-time reconstruction process consumes additional CPU and I/O resources, leading to a noticeable decrease in read and write performance until the failed drive is replaced and the array is rebuilt.
- ✗
The usable capacity drops to 2 TB until the drive is replaced.
Why it's wrong here
This statement is incorrect. For a RAID 5 array composed of three 2 TB drives, the usable capacity is 4 TB (N-1 drives * drive size). When one drive fails, the array's usable capacity does not decrease; instead, it enters a degraded state where it loses its fault tolerance, making it vulnerable to complete data loss if a second drive fails before the first is replaced and rebuilt.
- ✗
The array automatically switches to RAID 0 to maintain performance.
Why it's wrong here
This is incorrect. RAID levels are a fundamental configuration of the array and cannot automatically change dynamically, especially not to a level like RAID 0, which offers no fault tolerance. A RAID 5 array experiencing a single drive failure remains in a degraded RAID 5 state, relying on parity to reconstruct data, rather than abandoning its redundancy features for performance.
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
Troubleshoot: Storage and RAID
Key term
RAID 5
RAID 5 is a disk array configuration that uses block-level striping with distributed parity to provide fault tolerance and good read performance while using storage space efficiently.
Key term
CAN
A CAN (Controller Area Network) is a robust vehicle bus standard designed to allow microcontrollers and devices to communicate with each other without a host computer.
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Same concept, more angles
1 more way this is tested on 220-1201
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A technician is troubleshooting a server that uses a RAID 5 array with three 1TB HDDs. One drive fails, and the technician replaces it with a new 1TB HDD. After rebuilding, the array reports only 1.8TB of usable space. What is the most likely cause?
hard- A.The new drive has a different sector size (4K vs 512e).
- B.The RAID controller is using some space for metadata.
- ✓ C.The replacement drive has a slightly smaller actual capacity than the original drives.
- D.The RAID 5 array is degraded and needs a second drive to be replaced.
Why C: This question tests advanced RAID understanding. RAID 5 uses one drive's worth of capacity for parity, so three 1TB drives yield 2TB usable. The loss of 0.2TB suggests the replacement drive has slightly less capacity due to manufacturer differences or sector mapping.
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.