If someone wondered, how long it takes to copy a 3TB SATA drive to another identical SATA drive with 'dd', here's your fact:
dd if=/dev/sdb3 of=/dev/sda3 conv=noerror,sync
5855286143+16 records in
5855286159+0 records out
2997906513408 bytes (3.0 TB) copied, 106038 s, 28.3 MB/s
So it took 106038 seconds = 1767.3 minutes = 29.455 hours.
15 sectors of the input drive (/dev/sdb3) were defect, that's why I used "conv=noerror,sync" which allows to ignore the read errors.