rsync is very slow between the linux and additional secure HDD
I'm trying to copy the data between linux machine to an extra attached secure hdd, initially I mounted the secure hdd on the system. I have around 150GB of data to transfer in which there is tar file of around 132GB of size, I tried to copy the data by cp command. It broke frequently, then I tried with the rsync command. The rsync command it not breaking but its very slow, the rsync command is running from last three days continuously but still it transfered around 30% of the overall data.
Can somebody help to speed up the process of rsync.