NTP sync... doesn't

Following the instructions here, I've manually configured the Windows Time service to use an external time source.

As I noticed the server's clock drifts very fast (1s per 40min), I set the SpecialPollInterval registry parameter to 60sec so that it'll sync often thus neutralizing the drift.

The minute I executed net stop w32time && net start w32time the error dropped to 8ms and I was happy. Alas no more than 20min have passed and it is back up to 300ms.

How come?
How can I fix this?

Notes:

It's a VPS
Windows Server 2008
Using the following time sync sources: 0.pool.ntp.org, 1.pool.ntp.org, 2.pool.ntp.org
Using this to measure the drift
Measured minute by minute , the drift is almost linear

Jonathan

Posted 2011-07-08T15:13:01.243

Reputation: 3 371

Did your time drift before? It sounds like you may have a motherboard real time clock chip issue, but not sure based on this info. – KCotreau – 2011-07-08T15:21:26.947

It's a VPS, so I don't have access to the hardware, but there's DEFINITELY a HW problem with it drifting so much. I'm trying to workaround replacing my VPS with NTP sync – Jonathan – 2011-07-08T15:25:38.143

Answers

I would comment here, but compare your settings to the following server, which I know works. I have to add them as screenshots. I might also consider using the time.windows.com server. It may be farther than the ones you chose, but I have seen issues with other NTP servers. It will still get you close enough time-wise.

enter image description here

KCotreau

Posted 2011-07-08T15:13:01.243

Reputation: 24 985

Thanks you, it was the PollInterval which wasn't mentioned in MS's article. I set it to 60 sec decimal and it seems to have solved the problem – Jonathan – 2011-07-08T15:59:21.737

You're running your server in a virtual machine. All bets are off.

Virtual machines can have all sorts of fingers into the timekeeping of your server. What you're possibly witnessing is a fight between the Windows Time Service, trying to keep your machine synchronized with an NTP server out on Internet, and the virtual machine, trying to keep the guest operating system's clock in synchronization with the host operating system's clock. What's very probably causing this fight to be so blatant is that the host operating system's clock isn't set to the correct time. ☺

Details depend from what the virtualization software is, which you don't tell us. Microsoft's general advice for domain controllers, which really applies to any Windows 2008 Server computer and which Ben Armstrong expands upon as do several people on ServerFault (where you should be with server questions, by the way), is to turn off the guest-to-host synchronization and stick to NTP.

Notice that the Windows Time Service has ways of integrating the host operating system's clock as a second "time provider" in some virtual machines. Of course, if the host's clock is off you don't want to sychronize to it. ☺

JdeBP

Posted 2011-07-08T15:13:01.243

Reputation: 23 855