ESXi 4.1 w/2003 SBS, does the Windows Time service set the bios time?

Posted on 2011-03-10
Medium Priority
Last Modified: 2012-05-11
If I set up Net Time Service on a Windows 2003 Sever, running in ESXi 4.1, does it set the bios or only read it?
Question by:MikeBroderick
LVL 30

Expert Comment

ID: 35094771
no it wouldn't as esx controls the bios so the vm server couldn't set it it will only do the virtual bios clock see what I mean

Expert Comment

ID: 35094790
VMware Tools Time Synchronization and Configuration

When using w32time or NTP in the guest, disable VMware Tools periodic time synchronization.

To disable VMware Tools periodic time sync, use one of these options:

    * Set tools.syncTime = "0" in the configuration file ( .vmx file) of the virtual machine.


    * Deselect Time synchronization between the virtual machine and the host operating system in the VMware Tools toolbox GUI of the guest operating system.


    * Run the VMwareService.exe -cmd "vmx.set_option synctime 1 0" command in the guest operating system. VMwareService.exe is typically installed in C:\Program Files\VMware\VMware Tools.

These options do not disable one-time synchronizations done by VMware Tools for events such as tools startup, taking a snapshot, resuming from a snapshot, resuming from suspend, or VMotion. These events synchronize time in the guest operating system with time in the host operating system even if VMware Tools periodic time sync is disabled, so it is important to make sure that the host operating system's time is correct. For more information, see Timekeeping in VMware Virtual Machines.
To ensure the host operating system’s time is correct for VMware ACE, VMware Fusion, VMware GSX Server, VMware Player, VMware Server, and VMware Workstation run time synchronization software such as NTP or w32time in the host. For VMware ESX, run NTP in the service console. For VMware ESXi, run NTP on the VMkernel.

I hope this will answer your question
LVL 28

Accepted Solution

bgoering earned 2000 total points
ID: 35094843
It would work with the "virtual" BIOS in the virtual machine just as it would if Windows was running on a physical box, however the "real" BIOS Clock on the machine ESXi is running on won't be touched.

In a Windows domain environment I would suggest you allow your Windows DC that has the PDC role (that is the authoritive time source for a domain) sync with some external NTP source, then configure your ESXi to Sync its time with the PDC emulator via NTP. That will get the real time clock updated.

Just make sure you don't also select the option in VMware tools to sync the guest time with the host, otherwise they will be fighting a bit and making minute corrections all the time.

Good Luck

Author Closing Comment

ID: 35094969
Thank you all for your contributions.

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