[ntp:questions] Cluster NTP configuration

Chuck Swiger cswiger at mac.com
Mon Jun 20 20:03:21 UTC 2011

On Jun 20, 2011, at 6:59 AM, Steve Tryon wrote:
> Synchronization to a tenth of a second is fine for my purposes.  All servers will be running RH 5.5.

You won't need to do anything special to get better than 10ms sync accuracy, much less 100ms.

> My concern is centered around a bad local clock.  If I lose my external connections, will a bad hardware clock start to cause large incremental corrections?

If ntpd is allowed to run for a few days, it will establish a calibration for the intrinsic drift of the local clock.  So long as that drift is roughly stable, your machines will continue to keep reasonable time even if they lose external connectivity for a while.

[ However, running under C1EST or other power-management states can do bad things to timekeeping, especially if your box does not have a P-state invariant TSC; also, running under a VM generally also causes problems with good timekeeping. ]


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