Sadly, it disappeared:
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINTS
sda 8:0 0 1,9T 0 disk
└─sda1 8:1 0 1,9T 0 part /home
sdb 8:16 0 298,1G 0 disk
sdc 8:32 0 111,8G 0 disk
sdd 8:48 0 931,5G 0 disk
nvme0n1 259:0 0 238,5G 0 disk
├─nvme0n1p1 259:1 0 36,9G 0 part [SWAP]
├─nvme0n1p2 259:2 0 201,1G 0 part /nix/store
│ /
└─nvme0n1p3 259:3 0 512M 0 part /boot/efi
am I supposed to write a /etc/mdadm.conf file?
I see that the nix module has the following option hidden(?):
enable = (lib.mkEnableOption (lib.mdDoc "swraid support using mdadm")) // {
visible = false; # only has effect when the new stage 1 is in place
};
I put it on my configuration with enable = true; to see what happens next.