TRAID Storage Pool - Adding a new HDD

[pobotrol]

Hello, I've created a TRAID Storage Pool on a single 10TB HDD, and stored some data on there.
I want to add another blank 10TB to the Storage Pool.

All the instructions I read say to edit the Storage Pool and select "Add a Hard Disk to Array", but I can't find this option anywhere.
There are options for Sync Speed, Repair, to Delete the Storage Pool and Create New Storage Pool, but nothing about "Add a Hard Disk to Array"

What am I missing?

[pobotrol]

Sorry, I should add I'm using an F5-221 on TOS 5.1.2.4

[Gremlin]

Has the new disk been inserted into the NAS?

Can you see it in "Storage Manager" > "Hard Drive" ?

[pobotrol]

Hi again Gremlin, thanks.
Yes, it is, and shows as Good and at the correct size The two drives are identical and showing as such.

[Gremlin]

In that case, go to Storage Manager > Storage Pool

Click on the Storage Pool 1

If you click on the down arrow (top right corner of highlighted Pool 1 block) you can see the make up of the Pool.

Above the highlighted Pool 1 block there are 5 buttons - {I THINK} click on <Edit> button, second from left, which should be available once the disk is recognised. {Otherwise it might be available on right hand button <more>}

<Create> <Edit> <Delete> <Settings> <More>

[pobotrol]

I wondered if it might be those, because second from the left and the right hand button are both greyed out.

[Gremlin]

Just a thought - have you checked make up of Pool 1? Maybe it was added automatically. (I can't actually remember what happened as I started with 3 disks.)

[pobotrol]

I definitely added it manually.
This is actually Storage Pool 2, as Storage Pool 1 has its own 1TB HDD and set as a single disk.

Storage Pool 2, the one I want to expand says:

Which all looks good AFAIK!

[Gremlin]

Not really sure why it would do that without user input, but OK.

[pobotrol]

It was definitely user input.

Have I done something wrong? Is it not OK to have two volumes, one single disk and one TRAID?