So I have a single drive zfs pool and I recently got a second identical to add a mirror drive to pool. It seems however I'm unable to add the new drive to the pool from the UI.

 

 

If I change the pool slot size to 2, add the new drive to the pool and go and start the array, it gives me a new device too small error. The 2 drivers are identical so this shouldn't be an issue? During all of this the FS selection is greyed out and acting like the pool only has 1 drive so it never changes to show to option to do a mirror.

 

 

If I instead change the FS on the first drive to auto before adding a second slot to the pool then add the second drive and start the array, the second drive isn't assigned to the pool and just remains unassigned.

After array start

 

 

 

If I set FS to auto before the second slot being added and add the second drive then I can set zfs up with a mirror with 2 drives. It still refuses to assign the second drive apon starting the array.

 

Nothing weird in the pool status either

 

 

Dont the 7.0.0 changelog say that you can add a mirror drive to a zfs pool? I even updated to 7.0.1 to try and fix this but nothing happened.

 

Do I just run zpool attach command in the terminal and hope for the best?
Do I have to recreate the pool and zfs partitions on both drives?

Please post the diagnostics.

Diagnostics

 

diagnostics-20250306-1908.zip

Post the output from:

fdisk -l /dev/sdb

 

# fdisk -l /dev/sdb
Disk /dev/sdb: 1.82 TiB, 2000398934016 bytes, 3907029168 sectors
Disk model: N700 2000GB     
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 33553920 bytes
Disklabel type: dos
Disk identifier: 0x00000000

Device     Boot Start        End    Sectors  Size Id Type
/dev/sdb1          64 3907029167 3907029104  1.8T 83 Linux

Here

That is using the old partition layout, when was that pool created? With zfs should be fairly recent.

 

For performance reasons, and for many years now, Unraid creates 1MiB aligned partitions for SSDs, so it will have a little less space, and hence the error.

 

I would recommend creating a new zfs pool with the other device, use zfs replication to clone the current data on the old pool to the new one, then add the old device to the new pool.

 

I could also see if it's possible to make Unraid accept an existing old layout in the new device, but it may be worse for performance.

The current pool/zfs formatting is only a couple days old. I was moving data and reformatting the drives as I had first one in use with xfs and wanted both on zfs with a mirror.

So the current pool was created in unraid 7.0.0 but it is 4 KiB aligned tho, idk why 🤷‍♂️

 

 

I'll try and create a new pool with the drive that is currently empty, transfer the data and try merging again then

Edited March 6, 20251 yr by dakoriki

Check the partition for the new device after creating a pool, but it should be 1MiB aligned, strange that one isn't, unless the device is reporting rotational.

I created a new pool with the empty drive and it shows 1 MiB aligned.

 

If you are talking about sd* names being rotational, yes it seems like after each reboot the sda, sdb,... are reassigned, idk why again 🤷‍♂️

I just meant if the device was reporting that it rotates, meaning the OS thinks it's an HDD, which would be very strange, but post the output from

 

cat /sys/block/sdb/queue/rotational

 

 

# cat /sys/block/sdb/queue/rotational
0

The drive had been assigned in the array with xfs before I got the second drive and started using zfs on the 2 drives. I dont think it would effect the drive anymore? I had it in the array before knowing how to use ssd's properly in unraid .

That shouldn't be an issue, since the array will also format SSDs 1MiB aligned, so not sure what happened there.

I made a new pool with the second drive, copied the data over from the first pool. Then I was able to add the first drive the second pool correctly. I wasn't considering that to be an option that could work because I had just previously made the first pool.
With the new correctly 1 MiB aligned pool I was able to combine the 2 drives in a zfs mirror.

Also the first time I got that overwriting warning in the UI while doing this