Setting up a RAIDed Swap Partition

[spflanze]

I have a highly customized procedure to install Ubuntu in an encrypted ZFS file system, and RAIDed drives. A description of the installation procedure can be downloaded here:

https://www.mediafire.com/file/2w8mdb96tbzslub/Ubuntu_22.04_Root_on_ZFS_Encryption.odt/file

I got Ubuntu working fine in most respects, but I was not able to configure the swap partition. The partition was created with the statements:

sgdisk     -n 2:0:+256G    -t 2:FD00 $SSD1
sgdisk     -n 2:0:+256G    -t 2:FD00 $SSD2

The swap configure attempt was done with the command sequence:

apt install --yes cryptsetup mdadm
mdadm --create /dev/md0 --metadata=1.2 --level=mirror \
    --raid-devices=2 ${SSD1}-part2 ${SSD2}-part2

This result of the last command above was the error message:

mdadm: super1.x cannot open /dev/disk/by-id/nvme-eui.002538ba11517132-part2: # # Device or resource busy
mdadm: /dev/disk/by-id/nvme-eui.002538ba11517132-part2 is not suitable for this array.
mdadm: super1.x cannot open /dev/disk/by-id/nvme-eui.002538ba11505423-part2: Device or resource busy
mdadm: /dev/disk/by-id/nvme-eui.002538ba11505423-part2 is not suitable for this array.
mdadm: create aborted

How does one make these partitions not busy? I cannot figure how it be busy because in the installation procedure I do not see anything done that would make it busy. They have not been used for anything up to that point.

Is the partition not suitable only because it is busy? Is the type FD00 (Linux Raid type) appropriate for a RAIDed swap partition? I also tried type BF02 which is the Solaris swap type, but I got the same resulting error.

[spflanze]

I abandoned trying to create swap partitions and dd swap with a swap file. The procedure I followed for doing this is at:
https://github.com/zfsonlinux/pkg-zfs/wiki/HOWTO-use-a-zvol-as-a-swap-device