On Sat, Aug 22, 2009 at 3:28 PM, Aryanto Rachmad<[email protected]> wrote:
> I know that it is problematic to run ntpd on Xen domU, but could anybody > give me some suggestion to have a stable system clock? So, in virtual machines, "time" is variable. Your VM gets de-scheduled frequently, for tenths of a second at a time. Which makes timekeeping pretty tough. Even acurate CPU utlization is near-impossible to measure from within a guest VM. The usual "solution" is to have the hypervisor (dom0 in the Xen case) run ntpd, and provide time to the guest VMs using a vendor-specific driver. For VMware, this driver bundle is called "VMware Tools". For the commercial Citrix XenServer, it's called "Xen Tools". For your VPS, you should talk to your hosting provider I suppose. In general though, virtualization is not very compatible with good time keeping. But you should be able to do better than three-second jumps.We generally see <100 ms offsets in guests on a very busy VMware ESX 3.5u4 cluster. See also: http://support.ntp.org/bin/view/Support/VMWareNTP The VMware whitepaper listed there goes deep into the problem of providing good time to guest operating systems. -- RPM _______________________________________________ questions mailing list [email protected] https://lists.ntp.org/mailman/listinfo/questions
