PPT-CSE 486/586 Distributed Systems

Case Study Facebook Haystack Steve Ko Computer Sciences and Engineering University at Buffalo Recap DNS Hierarchical servers Root servers toplevel domain servers authoritative servers CDN. 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. Security --- 2. Steve Ko. Computer Sciences and Engineering. University at Buffalo. Recap. Three . types of functions. Cryptographic hash, symmetric key crypto, asymmetric key . crypto. Cryptographic hash. 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,. 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. 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.. Case Study: Amazon Dynamo. Steve Ko. Computer Sciences and Engineering. University at Buffalo. Recap. CAP Theorem?. Consistency, Availability, Partition Tolerance. Pick two. Eventual consistency?. Availability and partition tolerance over consistency. New Trends in Distributed Storage. Steve Ko. Computer Sciences and Engineering. University at Buffalo. Recap. Two important components in a distributed file service?. Directory service. Flat file service. 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. Gossiping. Steve Ko. Computer Sciences and Engineering. University at Buffalo. Recall: Passive Replication. Request Communication. : the request is issued to the primary RM and carries a unique request id.. Leader . Election --- 2. Steve Ko. Computer Sciences and Engineering. University at Buffalo. Algorithm 2: Modified Ring Election . election . message tracks . all. IDs of nodes that forwarded it, not just the highest. 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 . 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.