In my Unraid server, I have a 24tb and a 20tb parity drive, and a 16tb and a few 14tb data drives. I just precleared a new 24tb drive, but when adding it to an available slot, I see the message at the bottom of message at the bottom of the 'main' page:

Stopped. Disk in parity slot is not biggest.

If this is a new array, move the largest disk into the parity slot. If you are adding a new disk or replacing a disabled disk, try Parity-Swap.

Can I add my new 24tb drive as a 'data' drive, or do I have to make it a second parity drive and copy parity data from my 20tb to the new 24tb, and use the 20tb as data?

Thanks in advance!

23 minutes ago, YaSo said:

have to make it a second parity drive and copy parity data from my 20tb to the new 24tb, and use the 20tb as data

This but you do not need to copy anything. When you install new drive, a parity build will start. Suggest you add the 20tb to array and put 24tb parity in it's place in same step so you only get hit with 1 parity build.

Thanks, I wonder if I buy a third 'largest drive' (another 24tb), will Unraid let me use THAT as a data drive, since I can only have two parity drives...

4 minutes ago, YaSo said:

Thanks, I wonder if I buy a third 'largest drive' (another 24tb), will Unraid let me use THAT as a data drive, since I can only have two parity drives...

You can have as many data drives as you want up to the max allowed in the array (currently 28) as long as none of them are bigger than your smallest parity drive.

2 hours ago, Veah said:

This but you do not need to copy anything. When you install new drive, a parity build will start. Suggest you add the 20tb to array and put 24tb parity in it's place in same step so you only get hit with 1 parity build.

I get an error when moving the 20tb parity drive (smaller of my two) to a data slot, and adding the new 24tb as a new parity (along side my existing 24tb parity drive...

"Array Operation

Stopped. Invalid expansion. You may not add new disk(s) and also remove existing disk(s)."

So DO I need to do a parity swap (copy from 20tb to new 24tb), or am I missing something, if I want to add the 24tb to the system in one step?

(again, thanks for the help in advance)

Edited December 27, 2025Dec 27 by YaSo
thanks in advance

I thought you could do both. Can get around that by using 'New Config' and assigning everything manually. Take a SS and be sure to assign array drives correctly and the two 24Tb hdds as parity. I think you will be able to choose the fs for the old 20tb hdd. Be sure to preserve your things by checking the boxes before starting... I cannot recall exactly what they are called.