How do I manually rebuild degraded RAID 1 Array from Apple Disk Utility?

Support Center

Knowledge Base
December 10, 2019

The following steps shows you how to use Apple’s Disk Utility to rebuild CalDigit T3 or T4 RAID 1 (mirror RAID) if one drive fails and causes the RAID 1 array degraded.

1. Launch Disk Utility, go to the degraded RAID array, and select the drive that is missing from the RAID 1 array.

2. Click the “Minus” button.

Select Missing RAID 1 disk in Apple Disk Utility

3. Click on the “Demote” button to demote the missing RAID disk from the array.

Arrow pointing to demote button in Apple Disk Utility with Missing RAID 1 disk selected

4. Click on “Demote” button from the popup window.

Demote confirmation window. Arrow pointing to Demote button

5. Physically remove the bad RAID disk from CalDigit T3 or T4 chassis. 6. Insert the new drive module that you obtained from CalDigit to T3 or T4 drive slot.

7. In Disk Utility, you will see a brand new disk in the list, drag and add it to the degraded RAID array. 8. Click on “Rebuild” button to trigger the RAID rebuilding. It may take several hours to rebuild the entire RAID array depends on the drive capacity.

Arrow pointing to newly listed disk member after being dragged to degraded RAID array set. Arrow pointing to rebuild button in Apple Disk Utility.

Rebuild progress window in Apple Disk Utility.

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