CompTIA Server+ (SK0-005)TroubleshootingMedium
A server administrator receives alerts that a critical application server is experiencing 'Input/Output (I/O) error' messages in its logs, and users report application slowness. Upon inspection, the administrator notes that the server's RAID 5 array shows one disk as 'failed' and another as 'predicting failure'. What is the MOST immediate action the administrator should take?
- AReplace the failed disk immediately.
- BPerform a full backup of critical data before any disk replacement.
- CRebuild the RAID array from scratch.
- DReplace the disk predicting failure and then the failed disk.
Show answer & explanationAnswer & explanation
Correct answer: B. Perform a full backup of critical data before any disk replacement.
With one failed disk and another predicting failure in a RAID 5 array, the array is in a highly vulnerable state. RAID 5 can only tolerate one disk failure. A second failure (which is highly probable with a 'predicting failure' status) would lead to complete data loss. Therefore, a full backup is the most critical immediate action to prevent irreversible data loss.
Why the other options are wrong
- A. Replacing the failed disk is necessary, but performing a full backup takes precedence due to the high risk of a second failure.
- C. Rebuilding from scratch would result in data loss and is not an appropriate action when data recovery is the priority.
- D. Replacing disks without a backup first is extremely risky; a second failure during rebuild or replacement would lead to data loss.
RAID 5 Double Fault
RAID 5 can tolerate a single drive failure. A second drive failure (a 'double fault') within the same array leads to complete data loss.
- RAID 5 uses parity for data redundancy.
- Can withstand one drive failure without data loss.
- Two simultaneous drive failures result in data loss.
Memory trick: Two drives down, data's gone around.