In my opinion you should NEVER use NTPD in a virtual machine..... Check out how NTPD works... it tries to adjust "software cycles"to "hardware cycles". "Hardware cycles" are a bit undefined in a virtual machine. Best way, in my opinion, is: - Adjust clock of host using NTPD. - Adjust clock of virtual machine to clock of host using the appropriate Vritual tools. (Vmware Tools etc). Regards, Carel From: [log in to unmask] [mailto:[log in to unmask]] On Behalf Of Zack Yovel Sent: maandag 30 mei 2011 20:57 To: Alain Péan Cc: Orion Poplawski; Jaroslaw Polok; [log in to unmask] Subject: Re: clock drift under Hyper-V 2011/5/30 Alain Péan <[log in to unmask]> Le 27/05/2011 18:17, Orion Poplawski a écrit : On 05/27/2011 12:14 AM, Jaroslaw Polok wrote: Hello On 05/26/2011 10:28 PM, Orion Poplawski wrote: On 05/26/2011 07:29 AM, Zack Yovel wrote: 1. Hyper-V does not support RHEL. The only linux distro it supports is SUSE. I'm running a couple of CentOS 5.6 instances under Hyper-V. Horrible clock drift issues, but otherwise okay. You may want to add: divider=10 clocksource=acpi_pm to kernel arguments in /etc/grub.conf to correct the clock drift problem. Doesn't help me. Thanks though. I would have thought that the Hyper-V timesync integration driver would help too, but not for me. Hyper-V does support RHEL, at least 5 (not yet 6 perhaps). See : http://www.redhat.com/promo/svvp/ But if you have clock drift, why don't you setup an NTP server inside your VM ? Alain -- ========================================================== Alain Péan - LPP/CNRS Administrateur Système/Réseau Laboratoire de Physique des Plasmas - UMR 7648 Observatoire de Saint-Maur 4, av de Neptune, Bat. A 94100 Saint-Maur des Fossés Tel : 01-45-11-42-39 - Fax : 01-48-89-44-33 ========================================================== As I noted in a different mail, I was wrong and Hyper-V does support RHEL, up to 5.5 (not 5.6, at least according to Microsoft.. http://www.microsoft.com/windowsserver2008/en/us/hyperv-supported-guest-os.aspx perhaps a small difference in 5.6 could cause the problem?).