[Dovecot] VMware and Time moved backwards

[Bjørn T Johansen]

Why not? I have been running ntp inside vmware for many years now, without any problems....

BTJ

On Wed, 21 May 2008 12:30:01 -0700
Peter Hessler <phessler at theapt.org> wrote:

> never ever ever run ntp on virtual hardware.
> 
> instead, run ntp on the host hardware, and tell the client to always 
> obey the bios clock.  I add "* * * * * /sbin/hwclock --localtime --hctosys"
> to my crontab for that.
> 
> 
> 
> On 2008 May 21 (Wed) at 20:27:09 +0200 (+0200), Robert Henjes wrote:
> :
> :Hi,
> :
> :I followed the discussions regarding the "time moved backward" problem
> :and the use of ntp in such cases. At our department we are running two
> :dovecot servers within an vmware server environment, and unfortunately
> :the timedrift (with ntpd active) exceeds sometimes up to 30 minutes
> :virtual drift within 10 minutes realtime (mostly into future). This is
> :due to some overcorrections within the TSC algorithms of the vmware
> :virtual machine.
> :
> :More information and some hints to workaround are documented here:
> :http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1420
> :
> :Nevertheless we are currently working on evaluating a stable solution by
> :doing some system measurements, which would be the best option to cope
> :with this problem, since the XEN environment seems to have a similar
> :issue.
> :
> :Running "ntpdate -u" as a cronjob is not an option due to two facts:
> :a) Time is moving quickly and may cause "major problems" ;)
> :b) It is not recommended by the vmware team itself as well
> :
> :We are currently considering two options:
> :a) Using the "clock=pit" kernel option, which may cause the system to be
> :to slow
> :b) using vmware tools and use only the ntp synchronisation of the host
> :(we have currently only little experience with this). Also vmware tools
> :are somewhat critical in case of updates. So our intention was to
> :use as less vmware specific things as possible within the virtual
> :machine, so only our host itself depends on vmware specific software.
> :
> :The question is, which option would you prefer? Is there another
> :solution beside the mentioned ones? 
> :
> :According to Timo's postings, workarounds within the dovecot itself to
> :cope with "time moved backward" problems are not planned yet to be
> :impelented.
> :
> :So best regards,
> :Robert
> :
> :
>