1. Lee Center Workshop, May 19, 2006 Distributed Objects System with Support for Sequential Consistency

2. May 19 th, 2006Lee Center Workshop2 Motivation Applications: Scientific Computing, distributed file-systems, etc. Distributed file-systems Enable process migration and check-pointing Commodity hardware clusters vs. High Performance Parallel Computers Issues: Global naming and lookup Scalability Reliability Data/Metadata consistency

3. May 19 th, 2006Lee Center Workshop3 Naming and lookup Provide a global namespace Prevent name collision Provide location transparency Redundancy of metadata Reliability and fault-tolerance Several locations for the same metadata Fast and reliable lookup Provide caching Distribute the workload

4. May 19 th, 2006Lee Center Workshop4 Filesystem hierarchy Root Directory Critical for the existence of the filesystem Directories Contain metadata Files Metadata Data Replicate metadata on a “virtual server” Set of physical nodes

5. May 19 th, 2006Lee Center Workshop5 Domain Name System Root Domains Contain metadata about node entries Nodes IP addresses Properties: Reliable Distributed Fast (caching)

6. May 19 th, 2006Lee Center Workshop6 Integrate the filesystem with DNS Define hostname for the filesystem: mojavefs.caltech.edu Files and directories are sub-domains. DNS lookup to locate replicas of files Use dynamic DNS to update entries

7. May 19 th, 2006Lee Center Workshop7 File lookup /home/crt/foofoo.crt.home.mojavefs.caltech.edu Name server DNS query Name server forward query to authoritative server for mojavefs.caltech.edu Name server forward to authoritative server for crt.home.mojavefs.caltech.edu Reply referral 131.215.44.185141.85.166.2

8. May 19 th, 2006Lee Center Workshop8 File lookup failure /home/crt/barbar.crt.home.mojavefs.caltech.edu Name server DNS query Name server forward to authoritative server for crt.home.mojavefs.caltech.edu Reply

9. May 19 th, 2006Lee Center Workshop9 Create a file /home/crt/barbar.crt.home.mojavefs.caltech.edu Name server DNS query for crt.home.mojavefs.caltech.edu Name server forward to authoritative server for crt.home.mojavefs.caltech.edu Reply DNS update bar.crt.home... 131.215.44.185141.85.166.2 update metadata for /home/crt create /home/crt/bar

10. May 19 th, 2006Lee Center Workshop10 Virtual server membership update Name server forward to authoritative server for crt.home.mojavefs.caltech.edu DNS update 131.215.44.187 141.85.166.2 131.215.44.185

11. May 19 th, 2006Lee Center Workshop11 Conclusion Distributed Objects System Novel idea to use DNS naming/lookup in a distributed filesystem Increased reliability Uses an existing infrastructure Provides scalability Provides a globally accessible solution