Clock synchronization quality on Windows Azure?

Question

I am looking for quantitative estimates on clock offsets between VMs on Windows Azure - assuming that all VMs are hosted in the same datacenter. I am gu

Answer 1

This is the classic problem of both distributed systems and virtual machines - clock skew.

One possible solution would be to use the Azure scheduler to ping an endpoint on each of your VM that would reset your clock - or at least tell you what the diff would be. That way, your skew would not grow, and you may even be able to calculate an offset for the communication delay. This way, you'd get to within milliseconds and not seconds.

Ofcourse, you could also go the other way, and have a service on the VM that periodically manages the clock by pinging out to some time server. I'm not sure if the hypervisor will let you mess with it's clock, but all you really need is an offset for your apps to consume.

Overall... never trust the clock on a VM, and certainly not over a distributed system. Note that this clock issue is part of active research in many universities. ie. https://scholar.google.com/scholar?hl=en&q=distributed+system+clock&btnG=&as_sdt=1%2C48&as_sdtp=