Backup to a remote file location using tar over ssh:
tar cvzf – /localdirectory | ssh ssh root@remotehostname “dd of=/remotefilename”

Backup to a remote tape device using tar over ssh:
tar cvzf – /localdirectory | ssh ssh root@remotehostname $(mt -f remotetapedevice rewind; dd of=/remotetapedevice)$

Restore from a remote file location using tar over ssh:
cd /
ssh root@remotehostname “dd if=/remotefilename” | tar zxvf –

Examples:
Backup:
tar cvzf – /boot | ssh ssh root@thisis.myserver.name “dd of=/backup/boot.tar.gz”
tar cvzf – /boot | ssh ssh root@thisis.myserver.name $(mt -f /dev/nrst0 rewind; dd of=/dev/nrst0)$
Restore:
ssh root@thisis.myserver.name “dd if=/boot.tar.gz” | tar zxvf –