Back in July 2019, I wrote a blogpost on managing Active Directory Time Synchronization on VMware vSphere. This blogpost details how to configure time settings for Domain Controllers running as virtual machines on top of VMware vSphere. This blogpost introduced the concept of advanced time synchronization configuration. Now it’s time for an update; both for vSphere and for time synchronization.

About advanced time synchronization configuration

Advanced time synchronization configuration is a method to effectively disable time synchronization for virtual machines on top of VMware ESXi hosts. To make this configuration change, a vSphere admin would add the following lines to the virtual Domain Controller’s advanced configuration options:

tools.syncTime = "0"
time.synchronize.continue = "0"
time.synchronize.restore = "0"
time.synchronize.resume.disk = "0"
time.synchronize.shrink = "0"
time.synchronize.tools.startup = "0"
time.synchronize.tools.enable = "0"
time.synchronize.resume.host = "0"

With the above configuration, the virtual machine wouldn’t even synchronize its clock to the ESXi host’s clock when it is resumed, vMotion’ed, rebooted, when it is snapshotted or when its VMware Tools service is restarted or its disk is shrunk.

What’s new in VMware vSphere 7U1

In VMware vSphere 7.0 Update 1 build number 16860138, released on October 6th 2020, VMware introduced a graphical interface for the above advanced time synchronization configuration.

This interface in vSphere 7.0 Update 1 exposes the VMware Tools VM time correction features​ as two simple options labeled:

• Synchronize at startup and resume (recommended)
• Synchronize time periodically

The default behavior of adjusting a virtual machine’s clock through the VMware Tools during various virtual machine operations is now exposed in the virtual machine’s Properties as a checkbox. This box is checked by default to reflect the default VMware Tools behavior. This is shown above.

Unchecking the Synchronize at startup and resume (recommended) option effectively instructs VMware Tools to assume that the administrator has consciously applied advanced time synchronization configuration.

With these options, there is no need anymore to get messy with the eight advanced configuration options for a virtual machine. For Domain Controllers and domain-joined devices who experience a highly reliable time synchronization and correction mechanism, both options should be unchecked.

Concluding

VMware vSphere 7.0 Update 1 makes managing time synchronization in Active Directory environments a lot easier! This is a small yet welcome change to those managing complex environment, that will carry forward into the next versions of VMware vSphere.

Too bad the change is so small, it was deemed unnecessary to call out in the  VMware vCenter Server 7.0 Update 1 Release Notes…

Further reading

What’s New with VMware vSphere 7 Update 1
Ensuring Accurate Time-Keeping in Virtualized Active Directory Infrastructure
Managing Active Directory Time Synchronization on VMware vSphere
The video of our Active Directory session at VMware VMworld 2020 is now available
vSphere 7’s vMotion interface notifies for time differences between vSphere hosts