Ryan Malayter wrote: > 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. > Only someone who was trying to sell VM systems would even bother - its way to simple to maintain the VM system as a client and make all of this noise in the wind.
Todd Glassey (as an Auditor). > > ------------------------------------------------------------------------ > > > No virus found in this incoming message. > Checked by AVG - www.avg.com > Version: 8.5.409 / Virus Database: 270.13.65/2324 - Release Date: 08/24/09 > 12:55:00 > > _______________________________________________ questions mailing list [email protected] https://lists.ntp.org/mailman/listinfo/questions
