I manage two 2012 Mac mini computers which serve as VMware Fusion hosts. They are nearly identical in most ways - quad Core i7 processors, 16 Gbytes RAM, 1 Tbyte drives, etc. Both Mac mini computers are configured to login automatically, launch VMware Fusion, and then automatically boot a guest virtual machine. One Mac mini computer runs a Windows Server 2012 R2 guest. The other runs a business class firewall appliance guest.
Recently I noticed that the clocks in the host Mac mini computers are lagging behind real time, even though their System Preferences are configured with "Set date and time automatically" enabled. By lagging, I mean that the Mac minis running VMware Fusion continuously with active virtual machines are losing time so that their clocks fall behind "actual time" as measured by my desktop Mac, my "atomic" wall clock, and the The Official NIST US Time: website. I note that all three time sources agree with each other.
Both Mac minis set their clocks to the correct time whenever they are rebooted, so I know that there is no network issue preventing them from setting their clocks. Their clocks fall gradually behind as they run. It seems that whatever process is supposed to adjust the time as the host Mac runs is not working for these two computers.
The Mac mini running Windows Server in its virtual machine lost 25 seconds in 8 days since a reboot. The Mac mini running the firewall in its virtual machine lost 2 minutes and 15 seconds in 7 days since a reboot. I first noticed the issue with the Mac mini running Windows Server two weeks ago. This morning I realized that the Mac mini running the firewall has the same issue.
I called Applecare Support last Sunday after I had rebooted the Mac mini running Windows Server and then let it run for a week, after observing the 25 second clock drift following the reboot eight days earlier. The support technician suggested that I reset the SMC (System Management Controller). On a Mac mini, that is accomplished by shutting down the Mac mini, and then disconnecting the power cord for a minimum of 15 seconds.
I reset the SMC on the Mac mini running Windows Server last Sunday evening. It is now Friday morning (4.5 days later). The clock on the Mac mini is approximately 1 second slow, which is within reasonable tolerances. I am not ready to declare victory yet.
I reset the SMC on the Mac mini running the firewall this morning. Time will tell (pun intended) whether the fix worked on that machine. I will report back in a week or so with the results.
Here are my questions:
1. Is anyone else running full-time virtual machines, where the host Mac's clock is drifting slow?
2. Do you know the cause of the clock drift? Can it be attributed to VMware Fusion?
3. Can anyone explain why the "Set time automatically" is failing?
4. Can you confirm that the "reset SMC" solution is the correct one?
5. Do you have an alternate (better) fix for this issue?
As I said, I will report back with the results of the SMC reset that I performed this morning. It may take a week.
