ntsysv on my CentOS terminal show both
Is it redundant to have both service to run at start-up?
They do different things.
It's common to run
The usual way is to run ntpdate before starting ntpd.
Ntpdate is not a service, but a command that sets the time from an ntp server. Then ntpd keeps the time synchronized. The reason for doing this is that ntpd exits if the time difference is too great.