Centos – Timesync on HyperV with CentOS 6.2

centoshyper-v-server-2008-r2time-synchronization

I've got a CentOS VM (release 6.2) running under HyperV. I have integration services installed (part of base now), and CentOS shows the current clocksource is hyperv_clocksource, however my time in the VM is about 10 minutes fast after a week of uptime. My understanding of the new IC and plugable clocksource is that this shouldn't happen any more. Is there any additional configuration necessary to get the plugable clocksource to "work?"

I know there are plenty of links about setting kernel options to PIT and various stuff like that, but those all seem to pre-date the integrated clocksource support, and as I understand it shouldn't be needed anylonger. Nor should ntpd nor adjtimex.

Edit: Was running 3.2 of IC (what ships w/Centos 6.2), upgraded to 3.3 today, machine has been up for 1 hour 22 minutes and clock is already 5 seconds fast. So I'm now running the latest IC and still have the same problem.

Best Answer

I've had this issue in the past and corrected it by tweaking the startup switches (notsc divider=10) and ntp settings: 

# grub.conf generated by anaconda
#
# Note that you do not have to rerun grub after making changes to this file
# NOTICE:  You have a /boot partition.  This means that
#          all kernel and initrd paths are relative to /boot/, eg.
#          root (hd0,0)
#          kernel /vmlinuz-version ro root=/dev/VolGroup00/LogVol00
#          initrd /initrd-version.img
#boot=/dev/hda
default=0
timeout=5
splashimage=(hd0,0)/grub/splash.xpm.gz
hiddenmenu
title CentOS (2.6.18-164.6.1.el5)
    root (hd0,0)
    kernel /vmlinuz-2.6.18-164.6.1.el5 ro root=/dev/VolGroup00/LogVol00 hda=noprobe hdb=noprobe notsc divider=10
    initrd /initrd-2.6.18-164.6.1.el5.img
title CentOS (2.6.18-164.el5)
    root (hd0,0)
    kernel /vmlinuz-2.6.18-164.el5 ro root=/dev/VolGroup00/LogVol00
    initrd /initrd-2.6.18-164.el5.img

Sample ntp.conf: 

tinker panic 0
restrict 127.0.0.1
restrict default kod nomodify notrap
server 0.vmware.pool.ntp.org
server 1.vmware.pool.ntp.org
server 2.vmware.pool.ntp.org
driftfile /var/lib/ntp/drift

Source:

Correcting Linux Clock Drift on Hyper-V on Server 2008 R2
http://hardanswers.net/correct-clock-drift-in-centos-hyper-v

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