Lecture7 - COT 5611 Operating Systems Design Principles...

Info iconThis preview shows pages 1–8. Sign up to view the full content.

View Full Document Right Arrow Icon
COT 5611 Operating Systems Design Principles Spring 2012 Dan C. Marinescu Office: HEC 304 Office hours: M-Wd 5:00-6:00 PM
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Lecture 7 - Wednesday February 1 n Reading assignment: the class notes “Distributed systems-basic concepts” and “Petri Nets” available online. n Last time n Process coordination ¨ Lost messages ¨ Time, timeouts, and message recovery ¨ Causality n Logical clocks n Message delivery rules ¨ FIFO delivery ¨ Causal delivery n Runs and cuts Lecture 7 2/16/12 2
Background image of page 2
Today ¨ Distributed snapshots ¨ Enforced modularity  the client server paradigm ¨ Consensus protocols ¨ Modeling concurrency – Petri nets Lecture 7 2/16/12 3
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Runs and cuts; causal history n A run  a total ordering R of all the events in the global history of a distributed computation consistent with the local history of each participant process; a run implies a sequence of events as well as a sequence of global states. See the lattice of global states. n A cut  subset of the local history of all processes. n Cuts provide the necessary intuition to generate global states based on an exchange of messages between a monitor and a group of processes. The cut represents the instance when requests to report individual state are received by the members of the group. n Not all cuts are meaningful. n The causal history of event e, is the smallest consistent cut of including event e. Lecture 7 4 2/16/12
Background image of page 4
Inconsistent cut  C1 is an inconsistent cut (why?) C2 is a consistent cut Lecture 7 5 2/16/12
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Causal history  The causal history of event e is the smallest consistent cut including event e Lecture 7 6 2/16/12
Background image of page 6
Chandy-Lamport snapshot protocol n The monitor, process p0 sends to itself a ``take snapshot'' message. n Let ps be the process from which pi receives the``take snapshot'' message for the first time. Upon receiving the message, the process pi records its local state and relays the ``take snapshot'' along all its outgoing channels without executing any events on behalf of its underlying computation;
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 8
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 02/15/2012 for the course COP 5611 taught by Professor Staff during the Spring '08 term at University of Central Florida.

Page1 / 17

Lecture7 - COT 5611 Operating Systems Design Principles...

This preview shows document pages 1 - 8. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online