220-1201 Practice Question: A technician is called to a data center where a…

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 drives have a different rotational speed.

  Why it's wrong here

  While a rotational speed mismatch between drives in a RAID array can potentially lead to performance inconsistencies, it is not the primary or most common cause of a significant slowdown immediately following a drive replacement and subsequent rebuild. RAID controllers are designed to manage drives with minor variations, and the rebuild process itself is a far more demanding and direct contributor to temporary performance degradation. The array would likely operate at the speed of the slowest drive, but the rebuild's I/O demands are the dominant factor.

• ✓

  The array is still rebuilding in the background, consuming I/O resources.

  Why this is correct

  After a drive replacement in a RAID array, the controller initiates a lengthy rebuild process to reconstruct the lost data onto the new drive. This operation is highly I/O intensive, requiring extensive reading from the remaining healthy drives and writing to the new one, often with parity calculations. This background activity consumes a significant portion of the array's available I/O resources and processing power, directly competing with normal application requests and inevitably causing a noticeable slowdown until the rebuild is fully completed.

• ✗

  The RAID controller cache battery is dead.

  Why it's wrong here

  A dead or failing RAID controller cache battery primarily impacts write performance by forcing the controller to disable write-back caching and operate in write-through mode. This prevents data loss in the event of a power failure but significantly slows down write operations. While this is a performance issue, it is distinct from the broad I/O contention experienced during a post-rebuild slowdown, which is a direct consequence of the intensive data reconstruction process rather than a caching mechanism failure.

• ✗

  The stripe size was changed during the rebuild.

  Why it's wrong here

  Stripe size, also known as block size, is a fundamental configuration parameter established when a RAID array is initially created. It defines how data segments are distributed across the member disks. Changing the stripe size requires a complete re-initialization and re-creation of the entire RAID array, which would result in data loss and is not a modification that occurs automatically or can be performed during a routine background rebuild operation after a single drive replacement. Therefore, it is not a factor in a post-rebuild slowdown.

Go deeper

Related to this question