Re: [Qemu-devel] time synchronization with qemu

[giovanni bracco]

On Tuesday 14 September 2004 17:28, Gianni Tedesco wrote:
> On Tue, 2004-08-31 at 14:21 +0200, giovanni bracco wrote:
> > I have tried to use qemu to emulate a cluster of 3 linux boxes used as
> > AFS cell server system (RH 8.0 in my case) on a  SUSE 9.1 host system.
> > More o less it works but I have a problem with the time synchronization
> > of the 3 boxes.
> > AFS deamons require that the 3 servers have the same time but I have not
> > found a reasonable strategy to obtain that reliably.
> > Any suggestion?
> >
> > Is there a way in which the emulated system inside qemu can keep the time
> > of the host system?
>
> The same way you do it with real computers....
>
> Usually that means NTP or something.

I have tried but it does not works well and  I think that the reason is that 
inside a qemu system the clock is not stable and depends on the load of the 
host machine (which depends, in my case of the 3 qemu running together, also 
on the load on the other qemu systems). I suppose that ntp does not work well 
with very unstable clocks!

Up  to now the best solution I have found is to run a cron job on the host 
which sets every minute the clock of the 3 qemu systems using "rsh rdate -s 
host.ip" but still the time difference between qemu systems is til between 3 
and 10 seconds (even if there is a reset about every minute!)

Any suggestion is welll accepted!

Giovanni

ps:
on the host machine, kernel 2.6.5, I set at the boot the option clock=pit 
becouse otherwise the first qemu that I start runs a clock faster that the 
real clock of the host while the other two run slower. 
With clock=pit option all the three qemu run slower than the host and so the 
intrinsic time diffrence between them is lower.

-- 
Giovanni Bracco
ENEA INFO 
(Servizio Informatica e Reti)
Via E. Fermi 45
I-00044 Frascati (Roma) Italy
phone 00-39-06-9400-5597
FAX   00-39-06-9400-5735
E-mail  address@hidden
WWW http://fusfis.frascati.enea.it/~bracco