Consider creating a linear mode RAID with single disk(more disks may be added later).
#echo y | mdadm --create /dev/md0 --level=linear --raid-disk=1 /dev/sda1 --force
Now consider another partition is available , is it possible to "grow" from linear mode to RAID1(mirroring) mode? I can do something like this before for raid1 to raid5 , but for linear to RAID1 I have observed this error.
// change the level echo raid1 > /sys/block/md0/md/level "linear does not support online personality change"
I am aware about taking backup of existing contents of linear mode contents and then creating RAID1 with two partitions(one from span and another one newly added ) But, I am interested in doing it in place.