[CentOS-virt] ntp on kvm

Mon Jul 20 23:41:24 UTC 2009
Johnny Tan <linuxweb at gmail.com>

We've noticed our fully-virtualized KVM guests' time keeps 
getting faster, despite running ntpd.

A quick google reveals this to be a known problem with 
virtual guests. It seems there are a variety of solutions, 
some apparently vendor-specific.

What is the best practice as of now for KVM guests?

* Setting independent_wallclock=1 (or is that a xen-only thing)?

* Passing kernel parameters? If so, which? The vmware KB 
mentions "notsc divider=10" -- is that vmware-specific?

* Just don't run ntpd on virtual guests? And let it get its 
time from the host.

The last seems like the easiest/cleanest, if it really does 
always get its time from the host.

Thanks for any info.