220-1201 Practice Question: A small office server uses RAID 5 with three 1 TB…

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

• ✗

  The new drive is not the same model as the others.

  Why it's wrong here

  While mixing drive models in a RAID 5 array is generally permissible, it is unlikely to be the primary cause of an extreme system slowdown during a rebuild. RAID controllers are designed to accommodate drives of varying models, as long as they meet the minimum capacity and interface requirements. Performance might be capped by the slowest drive, but the inherent I/O intensity of the rebuild process itself is a far more significant factor for such a drastic performance impact.

• ✗

  The RAID controller is overheating.

  Why it's wrong here

  Overheating of the RAID controller, while a serious issue, typically manifests as system instability, random reboots, data corruption, or complete controller failure. It is less common for overheating to cause a gradual, extreme slowdown specifically during an I/O-intensive rebuild operation without other more critical symptoms. The scenario points more directly to a process-specific bottleneck rather than a hardware thermal issue.

• ✓

  The rebuild process is consuming all available disk I/O.

  Why this is correct

  A RAID 5 rebuild is an extremely I/O-intensive operation because the controller must read data blocks from all remaining operational drives, perform complex XOR calculations to reconstruct the missing data and parity, and then write that reconstructed data to the new drive. This simultaneous read-modify-write operation across multiple drives places an immense load on the disk I/O subsystem. This can easily saturate the array's available bandwidth, leading to a noticeable and severe performance degradation for all other server operations.

• ✗

  The new drive is not properly seated in the bay.

  Why it's wrong here

  If a new drive were not properly seated in its bay, the electrical or data connections would be intermittent or completely absent. This condition would typically result in the drive not being detected by the RAID controller at all, or it would immediately fail during initialization, preventing the rebuild from starting or causing it to fail instantly with critical errors. It would not manifest as a gradual, extreme slowdown during an ongoing rebuild process.

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