For copying disks, an even more powerful tool is ddrescue. It works exactly like dd but writes its progress into a map-file that can be used to pause and resume

For copying disks, an even more powerful tool is ddrescue. It works exactly like dd but writes its progress into a map-file that can be used to pause and resume the operation any time. It can also skip certain sectors known to be broken. Super useful if you have a big slow disk that you have to copy under unreliable conditions. Saved my ass several times with old partially broken hard drives.