1. Distributed P2P File System
By Cathy Chen

2. Project Objective
Implement a distributed file system with file replication, nodes failure management and basic file operations including locating, publishing, downloading and deleting a file from the system

3. System Components Service discovery File replication Caching
Downloading

4. Service Discovery Chord (Distributed Hash Table) Operations
Use basic hash function, SHA-1 to gerenate the 160 bits key for a given file name or a given node info
Operations
JoinChord
LeaveChord
FindChordSuccessor
ChordPublishFile
ChordDelFile
ChordLookupFile

5. Replication Motivations Replication Policies Increase fault tolerance
Increase availability
Load balancing
Replication Policies
Replicate 2 copies of the original file in the system
Replicated servers are chosen based on the shortest path
Only primary owner of the file can update files
Server-initiated update
Primary server will maintain the consistency of replicas and cached data

6. Client Cache Motivations Caching Policies
Improves performance by decreasing demand at the server
Better use of system resources
Caching Policies
Least recently used (LRU) algorithm
Server-initiated update
Primary server keeps a file index table with which block of the file is in cache at which node to maintain consistency

7. Downloading Use Chord to locate file
Determine which node to download blocks
Sequential Downloading
For small files
Parallel Downloading
10 threads
One thread per block

8. Basic System Architecture (Running Environment)
start the node based on a given topology file which describes a network topology along with link delays
keep track of whether a node is running or is down
maintain the shortest path table according to the up or down status of servers (using Dijkstra’s Algorithm)
handle communications between nodes (using RMI)
Maintain file organization (including directory structure for published files and downloaded files)

9. Implementation Environment
Design Languages
Java / RMI
Design Tools
NetBeans 5.5
System Environment
Linux
Window