Today I was converting some local virtual machine storage from LVMs to .img files on remote host. One can copy block devices over the network using SSH with a command like this:
dd if=/dev/vg/logicalvolumehere bs=1500 | ssh user@remotehost dd of=/path/on/remote/host.img
… or one could pass it through gzip first to compress the data as it goes over the network.
dd if=/dev/vg/logicalvolumehere bs=1500 | gzip -c | ssh 10.3.2.3 gzip -dc \| dd of=/path/on/remote/host.img
Running the transfer through gzip, I was able to get a speed of 16.6 MB/s or about 133 megabits/sec. over a 100 megabit network.