Simple PEer to peER File System (SPEERFS)

1. Simple PEer to peERFile System(SPEERFS) Done by: Assaf Waksman Benny Pano Supervised by: Uri Schonfeld On Spring 2005

2. Background • P2P – A way of sharing information among many equal work stations • File System – A database that supports and stores information units called files. • A need for sharable space that holds file-system instances arises: Achieves availability of information everywhere, as well as decrease in bandwidth load over a single server.

3. Objective Designing and implementing a distributed file system with a P2P approach. The system will let a user the ability to mount and use roots, which will be shared among the peers.

4. Considerations and Assumptions • The files are small • There are no sudden crashes of peers • A peer’s bandwidth is of domestic type • There are no simultaneous reads and/or writes to the same file (not including directories)

5. System’s goal characteristics • Scalable P2P network • Maintain data integrity • Equality among peers • Support basic FS operations needed by the OS • Ease of use

6. SPEERFS Architecture overview Create / Delete roots Create / Delete / Write / Read roots, files, directories Interface / Driver File-System Find a value’s holder P2P

7. NFS Protocol • Client  Server relationship • Gives the ability for remote users to mount a file system that populates the server • Uses the RPC mechanism • Supports {READ, WRITE, CREATE, REMOVE, MKDIR, RMDIR, READDIR, etc.} remote procedure calls

8. Chord Protocol • Each peer has a unique value. • Each peer has a successor and a predecessor in the network. • A peer is responsible for a values’ range between his predecessor and himself. • When a new peer joins the network, his successor’s responsibility range is updated accordingly.

9. Chord Qualities • Maintains scalability • Search for a value: O(logN) • Join / departure of a peer: O((logN)^2) • Maintains data integrity and organization

10. Chord Demonstration

11. File-System’s Data Structures • Every file in the file system is physically stored by the appropriate peer, according to the chord protocol. • Each peer has a database file that holds a list of all the files stored by this peer. • Each directory in the file system has a physical database file that contains a list of all the content of that directory. • The system supports passwords enforcement.

12. System’s Packages Were made: • chord – supports the ChordPeer class • com – supports communication operations • misc – stores helper classes • scome – supports the ScomePeer class Was altered: • nfsserver – implements an NFS server and contains the main method Was used: • org.acplt.oncrpc – implements the RPC mechanism needed by the NFS server

13. Major Classes • Peer – supports communication’s and basic peer’s functionality. • ChordPeer – inherits from Peer and implements the chord protocol. • ScomePeer – inherits from Peer and supports file system’s functionality. • Listener – Receives messages from other peers and initiates their handling.

14. Future Improvements • Handle simultaneous joins of peers to the chord network • Handle hostile messages • Support file links in the SCOME layer • Support multiple copies of files’ data • Limit the amount of data a peer can hold • Write a designated driver for the OS • Encrypt and compress messages and databases