NTP
Keeping time is important. Especially when debugging an issue between servers. It is a pain comparing logfiles with a time skew. For that reason we will configure two NTP servers that all clients will synchronize their clock to.
Configuring a redundant NTP server does not really make any sense. The DHCP server sends option ntp-servers to the DHCP clients, so if one NTP server is down, then the other will get the request instead.