Examkin

Question

Difficulty: HardStorage Drives and RAID Array Issues

A storage administrator is investigating an alert on a network-attached storage appliance configured with a hardware RAID 5 array of four 4 TB SATA drives. The management console reports the array is in a degraded state after one drive failed. The administrator inserts a brand-new, identical replacement drive, but the automated rebuild process fails to initiate, and the controller console displays an error stating that write-back cache has been disabled due to a depleted Battery Backup Unit (BBU). Which of the following is the most appropriate immediate action to safely allow the rebuild process to proceed?

  1. Restore or replace the controller Battery Backup Unit (BBU) to re-enable controller cache before initiating the array rebuild.Answer
  2. B
    Delete the existing array configuration and recreate a RAID 0 volume across the remaining active drives to bypass cache requirements.
  3. C
    Perform a full low-level format on all surviving member drives in the array to clear residual cache errors.
  4. D
    Replace the newly inserted replacement SATA drive with an M.2 NVMe PCIe solid-state drive.

Answer

The technician should restore power to or replace the controller's Battery Backup Unit (BBU) so that controller write caching functions normally, allowing the RAID parity rebuild to execute safely.
Hardware RAID controllers enforce safety policies that block rebuilds or force write-through operations when the Battery Backup Unit (BBU) or flash-backed write cache (FBWC) power source is depleted. Replacing or charging the BBU re-enables cache protection, allowing the controller to safely rebuild parity on the replacement drive.

Step-by-Step Solution

1
Analyze the controller warning message and failure symptom.
Identified that the rebuild process is blocked by the RAID controller due to a depleted or missing Battery Backup Unit (BBU), which forces write-through mode to prevent data corruption.
Hardware RAID controllers protect data integrity by disabling background parity rebuilds when dirty-cache protection is unpowered.
2
Select the proper corrective hardware maintenance step.
Replace or allow the BBU to charge fully, re-enabling write caching on the controller.
Resolving the BBU state clears the controller safety lockout without endangering existing array data.
3
Initiate the array rebuild process.
The array incorporates the new replacement drive and successfully calculates missing parity data to return to an Optimal state.
With cache protection active, the RAID engine safely executes intensive read/write operations for array reconstruction.

Key Concept

RAID Controller Battery Backup Unit (BBU) and Degraded Array Rebuild Policies
Rate this question

Topics

Storage Drives and RAID Array Issues

More questions from this topic