PPT-CSE 486/586 Distributed Systems

Consistency 3 Steve Ko Computer Sciences and Engineering University at Buffalo Recap Consistency Linearizability Sequential consistency Chain replication Primarybackup passive replication. Domain Name System. Steve Ko. Computer Sciences and Engineering. University at Buffalo. Last Time. Global states. A union of all process states. Consistent global state vs. inconsistent global state. Concurrency Control --- 3. Steve Ko. Computer Sciences and Engineering. University at Buffalo. Recap. Strict execution of transactions?. Delay . both their read and write operations . on an . object until . Google Chubby Lock Service. Steve Ko. Computer Sciences and Engineering. University at Buffalo. Recap. Paxos. is a consensus algorithm.. Proposers?. Acceptors?. Learners?. A proposer always makes sure that,. Graph Processing. Steve Ko. Computer Sciences and Engineering. University at Buffalo. Recap. Byzantine generals problem. They must decide on a common plan of action.. But. , . some of the generals can be traitors. Replication --- 1. Steve Ko. Computer Sciences and Engineering. University at Buffalo. Recap: Concurrency Control. Extracting more concurrency. Non-exclusive locks. Two-version locking. Reducing the lock overhead. Consistency --- 2. Steve Ko. Computer Sciences and Engineering. University at Buffalo. Linearizability. vs. Sequential Consistency. Both care about giving . an illusion of a single copy. .. From the outside observer, the system should (almost) behave as if there’s only a single copy.. Byzantine Fault Tolerance. Steve Ko. Computer Sciences and Engineering. University at Buffalo. CSE 486/586 . Administrivia. Project 3 out. Please, please start right away!. Deadline: 4/30 (Monday) @ 11:59PM. Reliable Multicast --- 2. Steve Ko. Computer Sciences and Engineering. University at Buffalo. Recap: Multicast. How do a group of processes communicate?. Multicast. One-to-many: “Local” broadcast within a group . Paxos. --- 1. Steve Ko. Computer Sciences and Engineering. University at Buffalo. Recap. NFS. Caching with write-through policy at close(). Stateless server. One power efficient design: FAWN. Embedded CPUs & Flash . Gossiping. Steve Ko. Computer Sciences and Engineering. University at Buffalo. Recap. Available copies replication?. Read and write . p. roceed with live replicas. Cannot achieve one-copy serialization itself. Mutual Exclusion --- 2. & Leader Election --- 1. Steve Ko. Computer Sciences and Engineering. University at Buffalo. 4. . Maekawa’s. Algorithm. Observation: . no need to have all peers reply. Only need to have . Web Content Distribution-. --3. Case Study: Facebook f4. Steve Ko. Computer Sciences and Engineering. University at Buffalo. Recap. Engineering principle. Make the common case fast, and rare cases correct. Paxos. --- 2. Steve Ko. Computer Sciences and Engineering. University at Buffalo. Recap. Paxos. is a consensus algorithm.. It allows multiple acceptors accepting multiple proposals.. A proposer always makes sure that,. Global States. Steve Ko. Computer Sciences and Engineering. University at Buffalo. Last Time. Ordering of events. Many applications need it, e.g., collaborative editing, distributed storage, etc.. Logical time.