1. Tempest: An Architecture for Scalable Time-Critical Services Mahesh Balakrishnan Amar Phanishayee Tudor Marian Professor Ken Birman

2. Clusters of commodity computers used in mission-critical settings (commercial and military) Advantages cost-effectiveness, incremental scalability and high availability Issues failures, arbitrary load, network losses affect real-time guarantees

3. Tempest: Goal Provide programmers replicated data storage primitives Very fast average performance and good worst-case timing guarantees Easy Deployment, Monitoring and Management of time-critical scalable services in a clustered environment

4. Tempest: Approach clone services for scalability, fault tolerance automate replica placement (service colocation) fine-grained data caching response time monitoring to detect service slowdown redundant querying for faster response UI to drag and drop services onto a cluster

5. Accomplishments Ricochet: Low-Latency Multicast for Scalable Time-Critical Services Submitted to NSDI 2006 (Oct 2005) Scalable Services Architecture (SSA) Submitted to ICDCS (Nov 2005)

6. Ricochet vs SRM SRM’s discovery delay is the lower bound on recovery SRM’s recovery delay scales poorly with # of Groups (delay in seconds!) Ricochet scales in # of Groups (~14ms in 1 group to 24 ms in 1024 groups) 64 Groups 9 seconds 64 Groups 16ms !

7. Ricochet vs SRM in 64 groups SRM Recovery centered around 9 seconds… Ricochet around 15 milliseconds. 1-2 orders of magnitude! Improvement increases with number of groups

8. Inconsistency Windows Ricochet Replication: Updates are reflected at all replicas within… 65% within 1.25 ms 90% within 18 ms 99% within 77 ms 100% within 125 ms