Windows – server virtualization: hypervisor (xen) or virtualbox

Guest Time Keeping in Windows under KVM Virtualization:

Virtualization poses various challenges for guest time keeping. Generally - Guests using the Time Stamp Counter (TSC) as a clock source generally suffer timing problems as some CPUs do not have a constant Time Stamp Counter.

I believe this is what is happening to you.

To clarify for others reading this post - guest systems without accurate timekeeping may have issues with some networked applications and processes as the guest will run faster or slower than the actual time and fall out of synchronization.

KVM works around this issue by providing guests with a para-virtualized clock. Alternatively, some guests may use other x86 clock sources for their timing in future versions of those operating systems.

To determine if your CPU has a constant Time Stamp Counter run the following command:

$ cat /proc/cpuinfo | grep constant_tsc

If any output is given your CPU has the constant_tsc bit.

Chances are however yours does not - and thus the issues your running into - therefore another work around / alternative is to first turn off any power management in the BIOS - as well as in the KVM.

It is also important to note that Windows uses the both the Real-Time Clock (RTC) and the Time Stamp Counter (TSC).

Older systems such as Windows 2003 and XP use the boot.ini file however - The boot.ini file is no longer used from Windows Vista and newer.

Windows 2008, Vista and 7 Booot Configuration Editor:

Windows Vista, Windows Server 2008 and Windows 7 use the Boot Configuration Data Editor (bcdedit.exe) to modify the Windows boot parameters.

1. Open the Windows guest.
2. Open the Accessories menu of the start menu. Right click on the Command Prompt application, select Run as Administrator.
3. Confirm the security exception, if prompted.

4. Set the boot manager to use the platform clock. This should instruct Windows to use the PM timer for the primary clock source. The system UUID ({default} in the example below) should be changed if the system UUID is different than the default boot device.

   C:\Windows\system32>bcdedit /set {default} USEPLATFORMCLOCK on The operation completed successfully

Windows 2003 and XP Boot Configuration Edit:

If by chance you are looking at this post - but the issue exists on your Windows XP and/or Windows 2003 system add the following line to the Windows boot settings. In XP and Server 2003 Windows boot settings are stored in the boot.ini file. Add the following line to the boot.ini file:

/use pmtimer

I really hope this helps.

Blessings, Glenn Kelley

Answers:

1. Ubuntu can be used as a dom0 host. I have used rhel5 as xen dom0 host on top of it i installed windows server 2k8 r2 and it works fine. I know rhel license is violated, but anyway i dont use rhel 5 support contract. i help myself and from the community. The steps i took to install xen on rhel with win serv 2k8 is documented in my blog in this url http://maximus2882.blogspot.com/2010/10/windows-2008-enterprise-on-rhel-55.html . Maybe that is of some use to you. It must be similar if not easier.
2. Xenserver does not install mdadm, it comes from the os package, in this ubuntu. You must do a #sudo apt-get install mdadm and use mdadm command to create RAID partition.
3. Multiple guest can share a same datastore but cannot share the same files. But can live in the same partition. the partitions and data in guest os is stored as files in host os. So they can happily share the same partition. I think there are ways to make a certain dir share between host os and guest os. I have done that in virtualbox in windows seven as host and fedora 14 as guest. Not sure how to do the same in xen , as i have limited with xen. I would suggest you go with vmware if you can. As my experience with vmware shows it is much matured and is the industry leader and has a smooth and consistent operation and interface that doesn't fail much.