How to properly rescue Ubuntu system drive?

Question

System administration

There is a server on Ubuntu with three disks.
The system disk with Ubuntu began to fail, and by the time it should have been replaced. What is the best way to do this to get everything the same?
You can use existing disks: there is enough space to mark the system disk image on them and boot from it.
In general, I understand what to do, but I don’t want to step on all the known rakes, I’m so unlucky.

Answer 1

1. from those disks where there is space, make a markup in the same way as it was done on the system disk.
2. copy everything from the old partitions to the new ones, like this:

rsync -axHAWXS --numeric-ids --info=progress2 / /mnt/newdisk

3. install the bootloader on the new drive

grub2-install /dev/new_disk

4. check fstab - that all mount points (first of all / , /var and other system ones) correspond to the necessary disks
5. control reboot