1. Distributed File Systems
Chad Griffith
Characteristics
Present Work
Future Work

2. Key Characteristics Dispersion of Users and Files
Multiplicity of Users and Files

3. Transparency (Dispersed Users)
Login Transparency
Uniform login
Uniform file system view
Access Transparency
Uniform file access, local or remote

4. Dispersed Files
Location transparency
Location independence

5. Multiplicity of Users Concurrency Transparency
File sharing between multiple concurrent users
NO adverse effects from this
Transaction based requires appearance of isolation
Concurrency control
Ensures concurrent execution of a transaction

6. Multiplicity of Files Files may be replicated for:
Redundancy
Concurrent access for efficiency
Replication transparency
Perform atomic updates on replicated files
Users only ”see” 1 copy of the file

7. Other Characteristics
Applies to DFS and distributed systems
Fault Tolerance
Scalability
Heterogeneity

8. Current Works TidyFS (Microsoft) For parallel computations on clusters
Emphasizes simplicity and small size
Has metadata server, node service, and TinyFS explorer
Tighter integration vs generality

9. Current Works GFS (Google file system)
Observance of app workloads and environment
Emphasizes large files and datasets
Appends new data vs modifying data
Co-designed with the applications that are to be run on GFS

10. Current Works HDFS (HaDoop) Large files and datasets
Streaming file access
No appending of files yet
Portability (more generalized)
Master/slave architecture

11. Current Works Tahoe-LAFS Peer to peer application
Pools HD space with friends
Auto encryption
Open source (GPL license)
Central node needed still

12. Future Works OS Independent DFS Communication independent DFS
Can detect file system and type and read from any system
Possibly can even learn about new file systems independently or from online accessible database
Communication independent DFS
File systems and communication systems will be more robust so that files can be accessed over different communications protocols

13. References
Distributed Operating Systems & Algorithms, by Randy Chow and Theodore Johnson, 1997.
hadoop.apache.org/