Slow delete and shutdown

Hi.

I'm replacing a disk in my system. I've added the new drive and I'm deleting one which is causing data to be written to the new drive. However, progress is painfully slow. 150GB of approx. 1.8TB written to new disk in about 12 hours. SO about 6 days to go. I know it is a slow process but this seems excessive.

I want to shut down the system in this period, would that be OK? Will it resume on boot or would I just re-issue the delete command?

Pete