NTP configuration best practices

• Always configure at least four time sources for NTP. In addition to providing redundancy in case one or more time sources becomes unavailable, The NTP protocol is designed to increase its accuracy with a diversity of sources. Even if your organization provides one or more local time servers, configuring additional remote servers is highly recommended for a robust setup.
• Pick servers in your server’s local geography. For example, if your servers are located in Europe, pick servers from the European NTP pool. If your servers are running in a public cloud environment, consult the cloud provider’s documentation for a recommended NTP setup. Many cloud providers offer highly accurate clock synchronization as a service.
• Use the iburst option for faster synchronization at startup. The iburst option instructs ntpd to send an initial "burst" of time queries at startup. This typically results in a faster time synchronization when a machine restarts.

An example NTP server list may appear as follows:

# Use my organization's internal NTP servers.
server ntp1.myorg.internal iburst
server ntp2.myorg.internal iburst
# Provide several public pool servers for
# redundancy and robustness.
server 0.pool.ntp.org iburst
server 1.pool.ntp.org iburst
server 2.pool.ntp.org iburst
server 3.pool.ntp.org iburst