Cassandra is quite interesting – and time sync seems increasingly critical to correct operation. Here are some resources: A paper on the storage model from developers at Facebook. A reasonably clear introduction from IBM Developer Works. A big difficulty for
Cassandra Cluster Synchronization
Cassandra is a highly-distributable NoSQL database with tunable consistency. What makes it highly distributable makes it also, in part, vulnerable: the whole deployment must run on synchronized clocks. It’s quite surprising that, given how crucial this is, it is not covered