[clug] October Canberra Linux Users Group meeting
michael at james.st
Tue Oct 20 23:38:10 MDT 2009
On 21/10/2009, at 3:40 PM, Alex Satrapa wrote:
> Please bring your laptops and experience/curiosity of virtualisation!
The biggest problem I've had with virtualisation is timekeeping.
On real hardware it's been a solved problem since the 90s.
Run ntpd with a good many servers in a loose network.
Kept the clocks accurate and was robust, using consensus
meant any server that went haywire was ignored.
In virtual bottles having the clock counting ticks doesn't work,
as the machine isn't there all the time and misses ticks.
Opensuse and SLES are bad at this, as they run the clock at 1000Hz.
In a guest, ntpd's assumptions about drift don't hold.
Running ntpd in multiple guests is an even bigger no-no
as they seem to fight over the clock.
?Does setting the hardware clock in a guest touch the hosts clock?
Anyway I've tried to run ntpd once in the underlying host OS,
but I haven't found the way to feed that time up into the guests
as an absolute value, not ticks that can be mis-counted causing drift.
My 2 seconds worth,
Well theme my emoticons disgusted. What has Linux come to?
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