Short summary on how to fully backup a disk over network using netcat and pv.
This solution is much faster than nfs or sftp but unencrypted. I experienced 112MB/s on my gigabit lan.
netcat -l -w 2 1111 | pv -b > backup.img
-s flag to provide an estimated size for pv to calculate ETA.
pv -s250G -cN "sda" /dev/sda | nc 10.10.10.1 1111