So now I have a second disk mounted, partitions cloned and UUID's randomised according to the guide.
This is now it looks now (sad is the newly added disk)
root@proxmox:~# fdisk -l /dev/nvme0n1 /dev/sda
Disk /dev/nvme0n1: 931.51 GiB, 1000204886016 bytes, 1953525168 sectors
Disk model: KINGSTON SNV2S1000G
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: 8EF1489A-8587-4274-8477-867F75F2A9C6
Device Start End Sectors Size Type
/dev/nvme0n1p1 34 2047 2014 1007K BIOS boot
/dev/nvme0n1p2 2048 2099199 2097152 1G EFI System
/dev/nvme0n1p3 2099200 1953525134 1951425935 930.5G Solaris /usr & Apple ZFS
Disk /dev/sda: 931.51 GiB, 1000204886016 bytes, 1953525168 sectors
Disk model: WDC WD10JPVT-22A
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: gpt
Disk identifier: 11986398-55BE-40E3-B9AE-9CBB0B31242B
Device Start End Sectors Size Type
/dev/sda1 34 2047 2014 1007K BIOS boot
/dev/sda2 2048 2099199 2097152 1G EFI System
/dev/sda3 2099200 1953525134 1951425935 930.5G Solaris /usr & Apple ZFS
Here is the final command (and error message). What am I missing?
root@proxmox:~# zpool attach -f rpool /dev/nvme0n1p3 /dev/sda3
cannot attach /dev/sda3 to /dev/nvme0n1p3: no such device in pool