220-1101 Question 405
Single answerRAID failureA small office file server uses a hardware RAID 5 array with three disks. Users report the server is much slower than usual, and during POST the RAID controller displays a message that the array is in a degraded state and one drive has failed. A replacement drive of the same size is available on-site. Which action should the technician take FIRST to restore fault tolerance while minimizing the risk of data loss?
- A
Replace the failed drive and allow the RAID controller to rebuild the array
- B
Reinitialize the RAID set so the controller can detect all drives again
- C
Replace all three drives to prevent another failure during rebuild
- D
Convert the array from RAID 5 to RAID 0 for better performance
Show answer and explanation
Correct answer: A
Explanation
A degraded RAID 5 array means one member disk has failed but the array remains operational using parity data across the surviving disks. The correct response is to replace the failed disk with a supported replacement and allow the hardware RAID controller to rebuild the array. This is consistent with common vendor guidance from manufacturers such as Dell, HPE, Lenovo, and RAID controller providers, which recommend hot-swapping or replacing the failed member and monitoring rebuild completion. Reinitializing, changing RAID levels, or unnecessarily replacing healthy disks can increase the chance of data loss. In A+ Core 1, candidates should recognize RAID 5 as fault tolerant for a single-disk failure, but also understand that the array is vulnerable until the rebuild completes, so restoring redundancy promptly is the priority.
- A. Correct.
Correct. In RAID 5, one disk can fail without immediate data loss because parity information is distributed across the remaining drives. When the array is degraded, the proper first step is to replace the failed disk with a compatible drive and let the controller rebuild the array. This restores redundancy and is the standard recovery action recommended by RAID controller and server vendors.
- B. Incorrect.
Incorrect. Reinitializing a RAID set typically destroys the existing array metadata and can result in data loss. A degraded RAID 5 array with only one failed disk is usually recoverable without reinitialization. Someone might choose this option if they confuse troubleshooting detection issues with a failed-drive rebuild procedure.
- C. Incorrect.
Incorrect. Replacing all drives is unnecessary and increases risk. The array is designed to tolerate a single drive failure, so best practice is to replace only the failed drive first. A technician might think replacing everything is safer, but removing additional working disks can complicate recovery and extend downtime.
- D. Incorrect.
Incorrect. RAID 0 provides no fault tolerance and converting an existing degraded RAID 5 array to RAID 0 is not an appropriate recovery step. This would not protect the data and could require reconfiguration that destroys the array. This distractor targets the misconception that performance should be prioritized over data protection during a failure.