/z Copies files in restartable mode. In restartable mode, should a file copy be interrupted, robocopy can pick up where it left off rather than recopying the entire file.
/r:<n> Specifies the number of retries on failed copies. The default value of n is 1,000,000 (one million retries).
/w:<n> Specifies the wait time between retries, in seconds. The default value of n is 30 (wait time 30 seconds).
If you are on Windows, take a look at Robocopy.