Why NTP is important for ESX/ESXi host?
it is very important the ESX/ESXi report accurate timings for following reasons
For accurate performance graph
For accurate timestamps in system logs
VM report accurate time if they are synchronizing their time with host
NTP client is default installed on ESX Host, but needs to be enabled. This client can be configured directly to talk with NTP server or can be configured to internal NTP Server.You can specific one or more NTP server.
hostd.log and messages are the log files where entries are made when ESX/ESXi boots and while system is up & running.
VMkernel,VMkwarning,VMKsummary.txt tracks service console availability.