I'm using Ubuntu Server 20.04 for testing purposes and yesterday was the backup day - hardly to say backup, just removing the second drive from the md
RAID 1, attaching it to another machine and then making full clone on another drive, then returning it again to the testing machine. Easy, not a problem to wait for the rebuild (10GB used space), but for production machine this is a no-go. Any ideas how to backup the whole installation (not the drives/partitions, only the used space) on external drive while the server is still running?
Thanks in advance