Network File System

Overview

This project implements a distributed Network File System (NFS) in C, supporting multiple clients, a central Naming Server, and multiple Storage Servers. The system allows clients to perform file operations (read, write, create, delete, list, info, stream audio) transparently across a distributed set of storage servers, with support for replication, asynchronous writes, and fault tolerance.

Architecture

+---------+         +----------------+         +------------------+
| Client  | <-----> |  Naming Server | <-----> | Storage Servers  |
+---------+         +----------------+         +------------------+

• Clients: User-facing programs that issue file operations.
• Naming Server (NM): Central coordinator that maintains the directory structure, maps files/folders to storage servers, and manages metadata, replication, and fault tolerance.
• Storage Servers (SS): Store actual file data and handle file operations as directed by the Naming Server.

Features

• File Operations: Read, write (sync/async), create, delete, copy, list, info, and audio streaming.
• Replication: Each file/folder is replicated to two other storage servers (when more than two are present) for fault tolerance.
• Asynchronous Writes: Large writes can be handled asynchronously for better client responsiveness.
• Concurrency: Multiple clients can access the system concurrently; only one writer per file at a time.
• Efficient Search: Trie-based directory structure with LRU caching for fast lookups.
• Failure Handling: Detects storage server failures and serves data from replicas.
• Logging: All operations and communications are logged for traceability.

File Structure

• naming.c — Naming Server implementation.
• storage.c — Storage Server implementation.
• client.c — Client implementation.

Compilation

You need a C compiler (e.g., gcc) and POSIX environment (Linux, WSL, etc.).

gcc -o naming naming.c -lpthread
gcc -o storage storage.c -lpthread
gcc -o client client.c -lpthread

Running the System

1. Start the Naming Server

./naming

• The Naming Server will print its IP and port (default: 8090).
• The IP is auto-detected using hostname -I.

2. Start Storage Servers

Each storage server must be started with:

./storage <Naming Server IP> <Naming Server Port> <Storage Server Port> <Accessible Folder>

Example:

./storage 192.168.1.10 8090 9001 ./data1
./storage 192.168.1.10 8090 9002 ./data2

• You can run multiple storage servers on different machines or ports.
• Each server registers itself and its accessible folder with the Naming Server.

3. Start Clients

Each client connects to the Naming Server:

./client <Naming Server IP> <Naming Server Port>

Example:

./client 192.168.1.10 8090

Client Commands

After starting, the client will prompt for commands:

• READ — Read a file.
• WRITE — Write to a file (optionally synchronous).
• CREATE_DIC — Create a directory.
• CREATE_F — Create a file.
• DELETE — Delete a file or directory.
• LIST — List files and directories in a folder.
• INFO — Get file metadata.
• COPY — Copy a file or directory.
• STREAM — Stream an audio file (.mp3 only; requires mpv installed).
• EXIT — Exit the client.

Example session:

Enter a command: READ
Enter file path: ./data1/file.txt
...
Enter a command: WRITE
Enter file path: ./data1/file.txt
Do you want to write synchronously irrespective of time overhead? (yes/no): no
Enter data to write: Hello, world!
...

Key Implementation Details

• Trie Directory Structure: The Naming Server uses a trie to efficiently map file/directory paths to storage servers.
• LRU Cache: Recently accessed paths are cached for faster lookup.
• Replication: When more than two storage servers are present, each file is replicated to two others for redundancy.
• Asynchronous Writes: Large writes are handled in the background, with immediate acknowledgment to the client.
• Concurrency: Mutexes and condition variables ensure safe concurrent access to files.
• Failure Handling: If a storage server goes down, the Naming Server marks it and serves data from replicas (read-only).
• Logging: All operations are logged in naming_server.log.

Error Codes & Handling

• If a file is not found, or is being written to, or a command is invalid, the client receives a descriptive error message.
• The system handles partial writes, server failures, and concurrent access gracefully.

Audio Streaming

• The client can stream .mp3 files using the STREAM command.
• Requires mpv to be installed on the client machine.

Assumptions

• All communication uses TCP sockets.
• IP addresses and ports are provided at runtime; do not hardcode 127.0.0.1.
• The system is designed for demonstration/educational purposes and may not be production-hardened.

References

• Project Specification
• POSIX C Library
• Handling Multiple Clients in C
• mpv Manual

Author

• Tathya Vaghasia

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