Linux RAID: add a hard drive to a working machine?

Question

linux

So, there is a home computer with one hard drive. There was a desire to add a second such hard drive to the "mirror".
Is it possible to make soft-RAID in such a way that you do not have to use a temporary intermediate hard drive to transfer data?
That is, I see it this way: I add a new hard drive to the computer, set it up, and wait for the data to be synchronized on these drives.
If this is not possible, then which option would be better in terms of reliability and ease of setup:

• use the utility to configure the built-in RAID controller (it's easy to set up, but you need another medium for temporary data storage; it is possible that this option will only work in Windows, because it works only through the driver, or look for the right module)
  
• make RAID using Linux OS (this is what I would like to know)
  

It will be very good if ready-made guidelines for just such a situation are found.
Here, in general, that's all.

Answer 1

You can transfer everything without data loss to a software raid. In short, you need to add a disk and mark it, create raid 1, designating the second disk as a miss and then synchronize, or you can copy everything, mark partitions instead of Linux as a raid. Several raids are created in this way for each of the sections. swap should also be included in the raid.
It seems the link on which is described correctly www.howtoforge.com/software-raid1-grub-boot-fedora-8