5 ms·
So that's exactly why you don't depend on hardware clocks -- you use software techniques when your algorithm depends on some notion of time. The point of Lampo
by chubot 12y ago
So that's exactly why you don't depend on hardware clocks -- you use software techniques when your algorithm depends on some notion of time.
The point of Lamport's paper is that time in distributed systems is a partial ordering, not a total ordering. If you are taking values from hardware clocks, you are using a total ordering.
- keeperofdakeys 12y agoYeah, but you can't have your clocks drifting a lot. It's fine if they are consistently wrong, but when a second isn't a second, things can start to screw up.
- judk 12y agoDoes Lamport's design use seconds at all, or use only "happens before" statements?
- tlarkworthy 12y agoGoogle spanner is a DB that uses atomic clocks distributed world wide. They seem to think the pain involved dealing with partial ordering is not worth the hassle given there genuinely is a total ordering on operations. http://en.wikipedia.org/wiki/Spanner_(database) http://en.wikipedia.org/wiki/Spanner_(database)
- dllthomas 12y ago"given there genuinely is a total ordering on operations." I thought relativity says there genuinely isn't (but it's close enough we can fudge it...)
- tlarkworthy 12y agoha! I think its ok as long as all parties involved are travelling on the earth and not around it near the speed of light http://en.wikipedia.org/wiki/Relativity_of_simultaneity http://en.wikipedia.org/wiki/Relativity_of_simultaneity
- dllthomas 12y agoRight. Like I said, we can (presently) fudge it. When we get moving faster that ceases to be the case.