I have an array with 2 parity disks.

I would like to add a data disk to the array without losing parity of the first parity drive,

in order to have redundancy while building parity 2.

Is the following procedure is correct?

 

1. Pre-Clear the new data drive.

2. Stop the array.

3. Add the new data drive.

4. Unassign Parity 2.

5. Check "parity is valid".

6. Start the array and format the new data disk.

7. Stop the array and reassign Parity 2.

8. Start the array.

 

This would rebuild Parity 2.

Would it also check the Parity disk or should I run another parity check after Parity 2 is built?

I am not sure why you think parity is affected when you add a new data disk unless something is going on that you have not mentioned.    If you have pre-cleared the drive then it does not affect either parity disk.   If you have not pre-cleared it then Unraid will Clear it as part of the process of adding it and again parity is not affected.

AFAIK Parity 2 is affected because it's parity algorithm includes the disk position.

The new data disk would be added as the 9th disk in the array, and it won't be the last one,

so some other disks would be reassigned to another slot.

7 minutes ago, Gico said:

AFAIK Parity 2 is affected because it's parity algorithm includes the disk position.

The new data disk would be added as the 9th disk in the array, and it won't be the last one,

so some other disks would be reassigned to another slot.

That is only relevant if you are trying to reorder existing disks!   Simply adding a disk does not affect parity.

OK. I will reorder existing disks. Is the procedure I wrote in the first post of this thread is correct?

7 hours ago, Gico said:

OK. I will reorder existing disks. Is the procedure I wrote in the first post of this thread is correct?

The procedure is correct if you WANT to reorder disks, but it is not clear from anything else you have said that this is the case.     Most people simply add a new data disk in the next available slot in the Unraid GUI so that no re-ordering is required.

 

it might be worth pointing out that re-ordering disks in the GUI has nothing to do with how they are physically connected.    Unraid recognises disks by their serial number, not by where they are connected.

Yes I want to reorder the disks as it helps me manage them:

Each group of disks contains a different media type.

Sequential disk numbers are easier to remember than random disk numbers.

Well that didn't work as planned because apparently moving a drive to another slot counts as removing and adding a drive,

and that's not allowed,

so I had to do a new config, and a full 2 parity drives parity rebuild is in progress.