Will mdadm delete data when creating raid 1 if there is information on one of the partitions?

Question

linux

Good afternoon! I want to make raid 1 in debian.
Tell me, please, read this Debian RAID manual for creating RAID 1.
It says that to create you need to run the command:

mdadm --create /dev/md0 --level=1 --raid-devices=2 /dev/hda1 /dev/hdc1

and then:
mkfs.ext3 /dev/md0
The next question. On one of the sections I have data, the other section is empty. Will the data be lost when executing these commands?

Answer 1

will be lost - there will be initialization of a new partition at the system level, and other "geometry" at a low level
ps even if you can then find something on the new volume, this will not be the norm, but rather an anomaly. save important data during any manipulations with file systems