What does migrating a large disk to a KVM image look like?

Question

System administration

The task is to transfer a large disk to the image, for its subsequent launch on a new server. What (for me) complicates the task, in addition to the lack of experience and the criticality of the data on the server:
Source machine

# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/md2             1016G   31G  934G   4% /
/dev/md1              496M   56M  415M  12% /boot
/dev/md3              1.7T  231G  1.4T  15% /home

* Target machine similar to original, but with proxmox as KVM manager
* Approximate 100-300 Gb KVM container (I don't need /home yet)
Here's what the migration process looks like in my wild imagination:

1. Boot on source machine in Rescue System mode
   
2. I cut GParted'om to 40 Gb [md2] and to 120 Mb [md1] - I do not touch md3
   
3. Mount md3 as image store
   
4. On the advice of proxmox , I use fsarchiver to make md2, md1 backups to files (on md3)
   
5. I decompress the disks to ~previous sizes, and reboot into normal mode
   
6. Sending and restoring images to disks/partitions of the target KVM machine
   
7. I spin the restored OS
   

Where am I delusional, what am I not seeing, and what “keywords
and phrases” should I google first?

Answer 1

isn't it easier?
tar -cjf backup.tar.bz2 / --exclude=/backup.tar.bz2
tar -xjpf backup.tar.bz2

Answer 2

And here, BuriK666 , everything is solved exclusively by grub?