[ntp:questions] ntp or other time stuff on virtual server?
david at ex.djwhome.demon.co.uk.invalid
Mon Nov 17 21:58:09 UTC 2008
> A question has come up on another newgroup whethr or not the time can be
> disciplined via ntp (or chrony) on a virtual server. I would suspect not
> (imagine the mess if both ntp on one virtual server and chrony on another
> were both trying to discipline the same hardware clock, and I cannot see
> how the virtual OS could keep track of its own separate clock since it only
> gets some subset of the time slices on the real system) but perhaps I am
> wrong. Can a virtual server discipline its own clock? If not, how is the
> adjtimex system call trapped? Surely each virtual machine cannot influence
> the real system, which is what would happen if the adjtimex call on each
> virtual machine were passed to the adjtimex system call on the real
You should discipline the host and run vmware tools or equivalent on the
guests. You should not run anything with tight timing requirements on a
guest, as the guest's time will have large short term variations because
the host will dish out time roughly in proportion to the CPU it gives.
A link to the VMWare paper on this was posted last week.
More information about the questions