Hi everyone. I am first time user and setup my Unraid. I previously with a 18TB drive, everything was fine and just added a 16TB into my NAS.

Now I have a weird storage display : volume has 17 TB / 7TB used / 3.96TB free. I can’t stop array because there is a btrf operation in progress and used capacity increasing progressively, now 8.3TB used. Wondering if this is normal and if not what should I do please ?

Thank you

Attach Diagnostics ZIP to your NEXT post in this thread.

tower-diagnostics-20250613-2115.zip

You added a drive to a single btrfs pool, by default that creates a btrfs mirror, I assume that's not what you want?

8 hours ago, JorgeB said:

You added a drive to a single btrfs pool, by default that creates a btrfs mirror, I assume that's not what you want?

Not really I would like to set parity, how can I change that without losing data ?

If you mean parity as in the array, you will need to remove the mirror from the pool, then reassign the original pool device to the array as data, and the new one as parity.

If the btrfs balance is still going on, cancel it with btrfs balance cancel /mnt/volume and post new diags.

2 hours ago, JorgeB said:

If you mean parity as in the array, you will need to remove the mirror from the pool, then reassign the original pool device to the array as data, and the new one as parity.

If the btrfs balance is still going on, cancel it with btrfs balance cancel /mnt/volume and post new diags.

Thank you so much.

But does it make sense with 2 drives ? I’m wondering if I should not just wait to have 3 drives and change the settings….

Don’t know what’s the best practice is.

It just depends on the use case, Unraid is very flexible, you can configure the server in many different ways, and most are not wrong, it's an option.

I would suggest using the unraid array for your disks. With that said you will need to make the 18TB disk your parity disk or get a second 18TB disk to make parity.

Edited June 14, 20251 yr by MowMdown

But If I change this, am I risking to lose data ? Do I need to delete my current array and create a new one ?

Thanks.

You can import the data from any single device pools, but not from mirrors, you would need to remove the new added disk from the pool first.

Got it and understand the mirroring.

Now if I want to come back to a normal configuration, what are the steps I need to perform please ?

Should I stop the array -> remove 16TB disk -> create new array -> add 16TB disk -> make 18TB disk parity ?

Thanks.

Post new diags to see the current pool status.

here it is.

tower-diagnostics-20250618-0538.zip

The first step is to remove the added pool device to return the pool to a single device:

https://forums.unraid.net/topic/46802-faq-for-unraid-v6/#findComment-480418

On 6/18/2025 at 2:54 PM, JorgeB said:

The first step is to remove the added pool device to return the pool to a single device:

https://forums.unraid.net/topic/46802-faq-for-unraid-v6/#findComment-480418

Thank you so much, I will do this week-end. Once pool will be back to single device, is there a tutorial explaining the options to change parity on the pool and all of this ?

Really checked everywhere and didn't find any, sorry to ask.

Thank you.

You can do a new config (Tools - New Config) to reassign the devices as you want, but any doubts, please ask first.

On 6/19/2025 at 5:24 PM, JorgeB said:

You can do a new config (Tools - New Config) to reassign the devices as you want, but any doubts, please ask first.

I followed the steps, there is only one drive now but BTRF operation is running for more than 12 hours and I get this message all the time

Warning [TOWER] - Cache pool BTRFS missing device(s)

It's likely still balancing, post current diags.

Just now, JorgeB said:

It's likely still balancing, post current diags.

Thank you so much. here it is.

tower-diagnostics-20250620-1852.zip

It's still rebalancing to single, 4TB to go, you can check the progress by clicking on the pool device, then scroll down to the balance status.

1 hour ago, JorgeB said:

It's still rebalancing to single, 4TB to go, you can check the progress by clicking on the pool device, then scroll down to the balance status.

Thank. When it will be done, I can setup the new config. No risk of losing data ?

Edited June 20, 20251 yr by pak888

Should be OK, but if you want, post the diags first to confirm the pool was correctly balanced.

On 6/20/2025 at 10:01 PM, JorgeB said:

Should be OK, but if you want, post the diags first to confirm the pool was correctly balanced.

Ok balancing done, I added the drive toi the pool but new config has done a full reset of the array and now I am afrfaid I can lose data or it will mirror again. No idea what to do.

I read this :
https://docs.unraid.net/unraid-os/manual/storage-management/
Actually I have the option to set in Array devices as below :

• Slots : 3

• Parity 1 : 18TB drive

• Parity 2 : unassigned

• Disk 1 : 16TB

My questions are :

• Is that ok to start array or will I lose all my data that currently rewsides in the 18TB drive ?

• Should I setup maximum slot for my NAS ? I can use 4 drives in the case, but having Parity 1 and Parity 2, I assume I would have to setup to 5 slots ? Or caqn I do this later and just set 3 slots for now ?

Thanks.

tower-diagnostics-20250622-0719.zip

Edited June 22, 20251 yr by pak888

9 hours ago, pak888 said:

Is that ok to start array or will I lose all my data that currently rewsides in the 18TB drive ?

You will lose the data from any device assign as parity, which devices have the data currently?