VirtualBox - Synchronisation problems

Question

I got VirtualBox running on Windows 7 host, running Ubuntu servers and XP-SP3 clients.

Often I note that the clock on the guest machines is strictly late in comparison to the host time. I first noted it when I got wierd benchmarking results for all kind of performance tests, and assumed that compare tests on the same machine to themselves would be OK - which is not.

The situation gets worse when client-server tests are involed. It might have been acceptable if all the guests would retain the same delay, but I run into situations where the time on the XP clients is more advanced on the servers, and situation that the time on the Ubuntu servers is more advanced then on the xp clients.

In a sense I could live with that - because it presents interesting test cases - but sometimes it gets to differences of 20 minuets.

I tried fidlling with the configuration for no avail - but I aught to be missing something...

Anybody? Thanks in advance.

Answer 1

If you have installed VirtualBox additions (and you probably have) there is a service on the guest host that syncs the time.

This service corrects the clock drift every 10 seconds if the difference between the host and guest clock is below 20 minutes, if the difference is above 20 minutes it just resets the guest clock to the host time. Thus you should never find a machine out of sync more than 20 minutes.

It is possible to change the 20 minute threshold using the --timesync-set-threshold guest parameter. You could for example set it to 1000ms, so you should never find a machine with a difference above one second.

You can configure the guest --timesync-set-threshold from the host machine using the following command:

VBoxManage guestproperty set <your-vm-name> "/VirtualBox/GuestAdd/VBoxService/--timesync-set-threshold" 1000

You should restart your guest additions service or your guest machine in order for it to take effect.

Further reading:

• Vbox manual. Check the section titled Tuning the Guest Additions time synchronization parameters
• This very useful post