There is a cool little trick to get the status of a dd operation out of the system. It will provide the status of dd via the err interface. You can do this one of two ways, either background (bg) the operation or perform it in a new terminal or screen.
For OpenBSD, a SIG_INFO (INFO) needs to be passed to the dd process:
pkill -INFO dd
For Linux, a SIG_USR1 (USR1) needs to be passed to the dd process:
pkill -USR1 dd
Both will produce the same output, it is just that the dd signals have been implemented differently. Output should look like:
303779673+0 records in
303779672+0 records out
311070384128 bytes (311 GB) copied, 96731.9 s, 3.2 MB/s
In the err output of the process terminal. The process will continue to run, without interruption