220-1101 Hardware and Network Troubleshooting Practice Question
A technician is troubleshooting a server with a RAID 5 array consisting of three hard drives. The server logs show a failed drive, and the array status is 'Degraded'. The technician replaces the failed drive with a new drive of the same model and capacity. After the rebuild process completes, the array status remains 'Degraded'. The server's OS does not show any new disk errors. Which of the following should the technician check NEXT?
⚠ Common exam trap
It's easy for candidates to assume a completed rebuild always restores the array to 'Optimal', overlooking the RAID controller's cache battery as a critical dependency for finalizing the array status.
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
✓
Check the RAID controller's cache battery status
After a RAID 5 rebuild completes but the array remains 'Degraded', the most likely cause is that the RAID controller's write-back cache could not be flushed to the new drive. A failed or missing cache battery forces the controller to operate in write-through mode, which can prevent the array from returning to a healthy state even after a successful rebuild. Checking the cache battery status is the correct next step because it directly affects the controller's ability to commit cached writes and finalize the array status.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Check the S.M.A.R.T. status of the remaining original drives
Why it's wrong here
While S.M.A.R.T. metrics such as reallocated sectors, pending sectors, or CRC errors are worth checking as part of ongoing drive health monitoring, the fact that the rebuild completed without read/write failures makes a remaining original drive failure an unlikely cause. If one of the original drives had actually failed or developed a fatal error, the rebuild would have failed or the array would still be missing that drive, not simply left degraded after a successful rebuild. The controller's cache battery, by contrast, directly controls whether the logical drive can be finalized after a write-back cache flush, so it is the more probable culprit.
- ✓
Check the RAID controller's cache battery status
Why this is correct
A failed or missing cache battery can cause the controller to keep the array degraded after a rebuild, as the controller may require a healthy battery to write cache data and finalize the array state.
- ✗
Check the firmware version of the new hard drive
Why it's wrong here
Firmware incompatibility or version mismatch on the replacement hard drive can prevent the controller from recognizing the drive, cause it to flag the drive as failed, or interrupt the rebuild with timeout errors, but it would rarely allow a rebuild to complete and then leave the array in a degraded state. Once the rebuild finishes successfully, the drive's firmware has already demonstrated compatible command handling and data transfer with the controller. A completed-but-degraded array is more consistent with the controller's inability to flush write-back cache due to a failed cache battery, rather than a drive-level firmware issue.
- ✗
Check the SAS cable connecting the drives
Why it's wrong here
A faulty SAS cable or damaged backplane connector typically manifests as missing drives, link resets, or CRC errors during negotiation, which would interrupt or fail the rebuild process completely. Since the rebuild completed, all three physical links delivered continuous, error-free transfers; a marginal cable would have caused dropped disk or inconsistent data during that operation rather than a clean completion. Even a partially defective cable tends to generate SCSI sense keys or enclosure management alerts that the controller would report, not a silent degraded status after a successful rebuild.
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.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 220-1101 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 220-1101 exam.