Distributed Objects System with Support for Sequential Consistency

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Distributed Objects System with Support for
Sequential Consistency
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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

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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

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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

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Domain Name System

• Root
• Domains
• Contain metadata about node entries
• Nodes
• IP addresses
• Properties
• Reliable
• Distributed
• Fast (caching)

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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

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File lookup
/home/crt/foo
foo.crt.home.mojavefs.caltech.edu
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File lookup failure
/home/crt/bar
bar.crt.home.mojavefs.caltech.edu
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Create a file
create /home/crt/bar
update metadata for /home/crt
/home/crt/bar
bar.crt.home.mojavefs.caltech.edu
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Virtual server membership update
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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