VM clock synchronization measurements

A modern twist to clock synchronization is the push towards server virtualization and cloud computing. Distributed applications now often run on geographically-distributed, virtualized servers that are isolated from the underlying hardware. Despite the fact that most applications run well in an abstracted environment without direct hardware access, tight real-time synchronized clocks are still necessary. We performed a set of experiments to quantify the additional clock error when running the NTP daemon inside a Virtual Machine. We found that the delay asymmetry is relatively small when running in a non-virtualized environment, but quite significant in a virtualized environment.