At 00:41 11-09-02, Len Thomson wrote: >1. There seems to be no nice way to get VM to maintain it's time synch >2. There seems to be no nice way to get a Linux guest to synch with the VM >time >3. I really don't want NTP clients all popping up at the same time to do a >network synch on every virtual server...
I admit I only briefly looked at the latest code, but afaik especially with the 'demand timer patch' Linux uses the TOD to tell time, and I don't recall seeing the drift corrections applied. This would mean an ntpd cannot adjust time of Linux running on z/VM, but one might be able to change that. I can even imagine hwclock to issue SCK instruction to update the virtual machine's private offset of the VM TOD clock (to live through a reboot, but not logoff). My understanding is that the S/390 TOD does not drift much, but we do have a problem of the operator setting time on VM by looking on his $10 Mickey Mouse watch. You're very right that you dont't want them all to measure time separately by talking to some remote ntpd. Howerver, I did see there is a lot of smartness in ntpd to increase the time between probes when it finds there is little drift. You could imagine one local ntpd to talk to a few good clocks, and have your local systems use that single server. It's on my list of things to do, so I would be interested in what others do (that is the fastest way these days for things from my list to get done ;-) Rob
