Time Synchronize on VM and ESX
Posted by craig - on August 25th, 2008 in Virtualization |
Time synchronize always important in every solution or platform. As ESX claim and advice the users to sync all the VM in ESX with the ESX host, I am here to explain why we shouldn’t do this.
- Recent major bugs from VMware had encountered exprie issue which disallow VM to be power on or Vmotion. What I had done personally is ” stop the NTP synchronization from esx host, and change the date back to 5 days back before the VM expire”. This easily solve my issue and allow me to Vmotion all the VM machine to another destination host without any interruption. Can you imagine if you sync all the VM with ESX host, you will lose this flexibility and in the big pain to figure out, how would you able to simplify the patch process to fix the bugs even VMware had released the bug fix
- I still do not see any potential issues with the current configuration that we sync all the VM and physical servers to multiple NTP servers we do have in our environment. Standardization always important as if we can minimize the different method of support and maintenance, it will help to reduce complexity.
- If you VM is running on windows, the VM will direct synchronize with the time servers in AD by default, and I don’t really see the potential need to create another specify way to synchronize the time on the VM.
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7 Responses
Our Windows machines are always in sync via AD as well, unfortunatly our Linux machines are not always so lucky, and we have had to implement the fixes found in this article :
http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1420
For VM running Windows, it is a best practice to sync time with ESX host via VMware tools as Windows Time Service does not work well in virtual environment.
For the Linux VM, you should try to sync through the NTP server in your environment. We are doing that in our environment now and we had put in 2 different NTP server as primary and secondary
Interesting, VMware told us NTP in guests under 3.02 -3.5 wouldn’t work. Are you using Redhat 4u5?
We used SLES9, SLES10 & RHEL3
sometimes we shouldn’t believe too much on all the best practices. Practical experience is more important and more suitable to your environment
I did a little more checking and I found out why it works for the versions of linux you mentioned, but not for the one we are running. It has to do with the Linux guest’s 2.4 kernel sending 1/10 of the timer interupts that 2.6 does, The time slip comes from the guest OS trying to respond to not being able to keep up with the interrupts. Apparently they have corrected the problem in the 2.6.18 release of the linux kernel.
So avoid the 2.6 kernels prior to 2.6.18 in your vmware environment if you can…