I want to upgrade a drive in an array from 16T to 24T.

I have added at 24T Parity drive and the parity sync process is complete. Now there are two parity drives.

I want to add one of these unassigned drives to the array:

I understand I must first remove the 16T Parity before I can add a 24T drive to the array.

So I stop the array and remove "Parity".

Then what is the exact process to "unassign" Disk 4 from the Array, and Assign Device Dev 1 in its place.

I want to end up with a 24T Parity, one 24T drive and 3 16T drives in the array.

I will physically remove the current 16T parity drive, so I'll end up with one Unassigned 24T drive.

Is this a standard "Drive Replacement" process? Will the 24T drive assigned to the array be automatically re-built with the correct data from Parity when the Array is started?

12 hours ago, timg11 said:

Is this a standard "Drive Replacement" process?

Yes

Thanks for your help. Last week I added a 24TB drive to the array as Parity2.

Once the parity was rebuilt, I unassigned the 16T parity drive.

I performed a Parity check, which took the amount of time to read a 24T drive, even though the Parity drive was the only drive with more than 16T capacity .

Today, I took the next step and completed the upgrade process with one 24 TB data drive.

I followed these steps

1.      Stop the Array: Stop the array via the WebGUI.

2.      Unassign Old Drive (Logical Slot): Navigate to Main à Array Devices. For Disk 4 (the logical slot you are replacing), change the assigned device to "No Device".

3.      Physical Removal: Remove the old drive from Physical Slot 4. (This is safe since the array is stopped, even with a hot-swap server).

4.      Assign New Drive (Logical Slot): Return to Main --> Array Devices. The entry for Disk 4 will show as "Not installed." Use the drop-down menu for the Disk 4 logical slot and select the 24TB drive that is currently physically installed in Physical Slot 8 and showing up as an Unassigned Device.

5.      Start the Rebuild: Click Start to begin the array rebuild process. Unraid will copy all the data that was on the old Disk 1 (which it is now emulating from parity) onto the new 24TB drive you assigned to the Disk 1 logical slot.

The physical slot location of the new drive (Slot 8) does not matter for the rebuild, only that you assign the correct drive to the correct logical slot (Disk 4) in the GUI.

Now the rebuild is underway

I selected Disk 4 because it had the least content on it.

So now the rebuild process is going. Will it take the amount of time to copy and rebuild the 3.49 TB of data, or the amount of time to copy 24T of mostly empty drive?

As I have the opportunity, I will purchase additional 24 T drives and repeat the process for Disk 1 to 3.

Edited October 27, 2025Oct 27 by timg11

13 minutes ago, timg11 said:

I performed a Parity check, which took the amount of time to read a 24T drive, even though the Parity drive was the only drive with more than 16T capacity .

This is normal.

13 minutes ago, timg11 said:

So now the rebuild process is going. Will it take the amount of time to copy and rebuild the 3.49 TB of data, or the amount of time to copy 24T of mostly empty drive?

It will rebuild the whole drive (24TB)

4 hours ago, JorgeB said:

It will rebuild the whole drive (24TB)

Sounds like a candidate for future enhancement of Unraid - although not critical since rebuild is hopefully an infrequent operation.

Although upgrading a larger array could literally take weeks to accomplish one drive at a time. 

9 hours ago, timg11 said:

Sounds like a candidate for future enhancement of Unraid

That's out it needs to be, it needs to rebuild all the disk to match parity, Unraid has no way of knowing what the content of it, if the disk has been previously used, for example, it won't be zeros.