Perhaps SSH? You can do something like:
ssh root@<your-server-ip> "sudo dd if=/dev/sda " | dd of=Downloads/disk.iso status=progress
Enter your password, or if you use SSH keys the command will run instantly. This command reads your entire disk or individual partitions bit by bit and pipes the output to your local disk. I opted for a iso file because I can easily mount that on my Linux client, but you can use any file extension, it's a raw disk image simply put.
