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Difficulty: Very hardStorage Drives and RAID Array Issues

A system administrator receives an automated alert indicating that a four-disk RAID 5 array on a critical enterprise server has entered a degraded status due to a disk read failure on Drive 2. Before a replacement disk arrives, a technician accidentally removes operational Drive 3 from the server chassis, causing the RAID volume to immediately go offline and become unmountable. The technician immediately realizes the mistake. Which of the following is the most appropriate immediate action to restore the volume to a degraded operational state without causing permanent data loss?

  1. Reinsert Drive 3 into its exact original drive bay slot and clear the offline flag in the RAID controller configuration interface.Answer
  2. B
    Re-initialize and re-create the RAID 5 array structure using Drive 0, Drive 1, and Drive 3 through the RAID controller BIOS.
  3. C
    Format all functional drives in the system and restore the degraded array configuration table from the RAID controller backup logs.
  4. D
    Convert the existing array metadata configuration to a RAID 0 volume across the remaining healthy drives to bypass parity validation.

Answer

Reinserting the accidentally removed healthy drive into its original slot allows the RAID controller to recognize the array as single-drive degraded, restoring volume mountability so data access can resume.
RAID 5 arrays distribute parity across all member disks and can only tolerate a single drive failure at any given time. When Drive 2 failed, the array operated in a degraded state. Removing Drive 3 introduced a second missing member, exceeding RAID 5 fault tolerance and causing the volume to go offline. Reinserting functional Drive 3 into its original slot returns the array to a single-drive failure status, allowing the controller to bring the volume back online in degraded mode until failed Drive 2 is hot-swapped.

Step-by-Step Solution

1
Analyze the array fault tolerance status
A 4-disk RAID 5 array can tolerate exactly one disk failure. Drive 2 failed (1 failure = degraded). Pulling Drive 3 created a second offline disk (2 failures = volume offline).
RAID 5 uses distributed parity and requires all member drives except one to function.
2
Identify the immediate corrective measure for the second drive removal
Because Drive 3 is physically functional and was only unplugged, reinserting it into its original bay restores the original single-failure (degraded) state.
Re-establishing connection for Drive 3 reduces active failures back from 2 to 1, returning the array to tolerance limits.
3
Clear controller status flags and verify volume access
The RAID controller marks the array back as degraded rather than offline, permitting the OS to mount the storage volume.
Destructive actions such as re-initialization or re-formatting must be avoided to preserve array metadata and block consistency.

Key Concept

RAID 5 Fault Tolerance and Degraded Array Recovery
Estimated Time:2m 0s
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Topics

Storage Drives and RAID Array Issues

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