PPT-Vector Clocks and Distributed Snapshots

COS 418 Distributed Systems Lecture 4 Wyatt Lloyd Today Logical Time Vector clocks Distributed Global Snapshots 2 Lamport Clocks Review Q a b gt Q LCa lt LCb gt . The theory of distributed systems shunned the notion of time and intro duced causality tracking as a clean abstraction to rea son about concurrency The practical systems employed physical time NTP information but in a best effort man ner due to the MANI CHANDY University of Texas at Austin and LESLIE LAMPORT Stanford Research Institute This paper presents an algorithm by which a process in a distributed system determines a global state of the system during a computation Many problems in distri Spring 2009. L. -9 . Logical Time. 1. Announcements. Project 1 update – Thursday. Due 2/26. HW 1 – due Thursday. 2. Last Lecture . –. Clock Sync Important Lessons. Clocks on different systems will always behave differently. Lecture 1. Main Characteristics of Distributed Systems. Independent processors, sites, processes. Message passing. No shared memory. No shared clock. Independent failure modes. CS 271. 2. Distributed System Models. Topics. Logical clocks. Totally-Ordered Multicasting. Vector timestamps. Readings. Van Steen and Tanenbaum: 5.2. Coulouris: 10.4. L. Lamport, “Time, Clocks and the Ordering of Events in Distributed Systems,” . 10/30/11. Ordering and . C. onsistent . C. uts. 1. Introduction. D. istributed systems. Loosely coupled processes cooperating to solve a bigger problem. N. ovelty of distributed systems. Lamport published his paper in . Time keeps on slipping, slipping…. Logistics. Last week’s slides online. Sign up on Piazza now. No really, do it now. Papers are loaded in . HotCRP. Sign up for account at . http://cs7780.ccs.neu.edu. Susmitha. . kota. . 21-sep-2015. AGENDA. Introduction. Synchronization. Physical Clocks. Global Positioning System. Algorithms. Future Work. References. Introduction: Real . Time System. EE324 Lecture 11. Assignment . Start early!. People who are doing well vs. Not doing well. . Last . Time–. RPC. Why remote procedure calls?. Simple way to pass control and data. Elegant transparent way to distribute application. Vector Clocks. Vector clocks overcome the shortcoming of . Lamport. logical clocks. L. (e) < . L. (. e. ’) does not imply . e. happened before . e. ’. Goal. Want ordering that matches causality. deepika. . gopala. . AGENDA. Introduction. Clock Synchronization. Physical Clocks. Global Positioning System. Algorithms. References. Introduction: Synchronization. Communication is important, but how processes synchronize and cooperate with each other is also important.. October 11, 2018. A.F. Cooper. Context and Motivation. How can we synchronize an asynchronous distributed system?. How do we make global state consistent? . Snapshots / checkpoints. Example: Buying a ticket on Ticketmaster. Time and Clock Time and Clock Primary standard of time = rotation of earth De facto primary standard = atomic clock (1 atomic second = 9,192,631,770 orbital transitions of Cesium 133 atom. Time and Clock Time and Clock Primary standard of time = rotation of earth De facto primary standard = atomic clock (1 atomic second = 9,192,631,770 orbital transitions of Cesium 133 atom.