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VSICM55 - Slide 02-44 - ESXi as an NTP Client



Room for improvement:

The third bullet in slide notes states:

Virtual machines can synchronize their time with the ESXi host.
Info:

As noted in the lastest "Timekeeping in VMware Virtual Machines" whitepaper, using the VMware Tools to correct long-time drift can be done yet it might be less precise, hence the need to run network clock synchronization software such as NTP or the Windows Time Service to keep time accurately over the long term.

In a physical machine, it is generally necessary to run network clock synchronization software such as NTP or the Windows Time Service to keep time accurately over the long term. The same applies to virtual machines, and the same clock synchronization software can be used, although it sometimes must be configured specially to deal with the less smooth performance of virtual timer devices. VMware Tools can also optionally be used to correct long-term drift and errors by periodically resynchronizing the virtual machine’s clock to the host’s clock, but it might be less precise.
[...] testing has shown that NTP in particular behaves fairly well in a virtual machine when appropriately configured [...]. NTP is prepared for some of its readings to be anomalous because of network delays, scheduling delays on the local host and other factors and is effective at filtering out such readings.
Generally, it is best to use only one clock synchronization service at a time in a given virtual machine to ensure that multiple services do not attempt to make conflicting changes to the clock. So if you are using native synchronization software, we suggest turning VMware Tools periodic clock synchronization off.
Source:

Timekeeping in VMware Virtual Machines.


Last modified onThursday, 12 December 2013 20:04
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