Physical and Logical Time: Closing Thoughts
Understand the key distinctions between physical and logical time in distributed systems, including how each measures and orders events. Learn the challenges and benefits of clock synchronization, the role of logical clocks like Lamport and vector clocks, and how these mechanisms help maintain consistency despite network partitions or clock drift.
Hopefully, the two previous chapters helped us understand the difference between the concepts of physical and logical time. At the same time, some parts went into detail to explain the inner workings of some techniques and their benefits and pitfalls. This might have left us with more questions, so this lesson will contain an overview of what we have seen and some additional observations.
Let’s start by reviewing the basic difference between physical and logical time.
Difference between physical and logical time
Physical time
Physical time is measured based on some physical phenomena. Depending on the phenomenon that is observed, the granularity of physical time can differ from days to seconds or nanoseconds.
In all cases, the time flows continually between discrete values.
Time can be considered discrete in the context of hardware or software systems. Whether this is true in other contexts (i.e., physics) is a much bigger question and is out of topic for this discussion.
-
In a non-distributed system, a computing node can use these measurements to associate occurring events and compare them with each other to determine which happened first.
-
In a distributed system, the various nodes have separate ...