Time synchronization for hosts running onVMWare - NTP

This is a discussion on Time synchronization for hosts running onVMWare - NTP ; I'm cross-posting this from the Kerberos mailing list since this is useful information for people running O/S's on top of VMWare and people come here for time issues. Danny -------- Original Message -------- >How about using the VMWare-Player for setting ...

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Thread: Time synchronization for hosts running onVMWare

  1. Time synchronization for hosts running onVMWare

    I'm cross-posting this from the Kerberos mailing list since this is
    useful information for people running O/S's on top of VMWare and people
    come here for time issues.

    Danny

    -------- Original Message --------

    >How about using the VMWare-Player for setting up various test machines?


    >Ciao, Michael.


    it's a good idea, but be careful with the time synchronization.
    Some guest OS consistently run more slowly or more quickly than real
    world time. The reason that caused the slowing time inside guest system
    is because of that the guest clock frequency is setting too high than
    the host OS can offer.

    And if you have a time problem Kerberos can't work properly, specially
    the ticket manager.

    If yours guest OS is Linux you have a workaround on the vmware's web
    site :
    http://kb.vmware.com/selfservice/vie...n_US&externalI
    d=1420

    if you want use FreeBSD check this link , but it's in French sorry,
    maybe it can help :
    http://casys.crevetor.org/index.php/...e-server_Guest

    --
    Thomas Boutry

  2. Re: Time synchronization for hosts running onVMWare

    I added this section to the NTP Wiki a few weeks ago to address
    similar questions:
    http://support.ntp.org/bin/view/Support/VMWareNTP

    We are wrapping up a large virtualization project at my office, and I
    was surprised how poorly virtual machines keep time. Note that this
    issue is not specific to VMware - all virtualization solutions have
    the same problem with time itself being virtualized (Xen, Microsoft
    Hyper-V, KVM, etc...)

    --
    RPM

  3. Re: Time synchronization for hosts running on VMWare

    On Jul 14, 11:29*am, malay...@gmail.com (Ryan Malayter) wrote:

    > issue is not specific to VMware - all virtualization solutions have
    > the same problem with time itself being virtualized (Xen, Microsoft
    > Hyper-V, KVM, etc...)


    That doesn't seem right. Some forms of virtualization virtualize the
    time in this manner, but some do not. For instance on a multiple
    processor system, any type 1 hypervisor like xen or Hyper-X should be
    able to keep the time just fine. With other types like VMware and
    Virtualbox that share the resources between the host OS and the
    virtual one, it only stands to reason that the time keeping will be
    shaky at best.

    Brian Utterback

  4. Re: Time synchronization for hosts running onVMWare

    On Sun, Jul 20, 2008 at 12:18 PM, wrote:
    > That doesn't seem right. Some forms of virtualization virtualize the
    > time in this manner, but some do not. For instance on a multiple
    > processor system, any type 1 hypervisor like xen or Hyper-X should be
    > able to keep the time just fine. With other types like VMware and
    > Virtualbox that share the resources between the host OS and the
    > virtual one, it only stands to reason that the time keeping will be
    > shaky at best.


    It seems Xen has the same issues as VMware... see:
    http://xen.org/files/summit_3/Xen_HVM_SMP.pdf

    Interrupts (including timer interrupts) are delayed, and/or batched
    with all x86 virtualization platforms of which I'm aware.

    --
    RPM

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