Boosting Developer Workflows with Mutagen

Introduction

 In distributed environments, accessing files over NFS-mounted directories relies on direct network connectivity and latency from remote locations, especially when a researcher or developer works over a VPN or from a different region.

These delays can create a poor user experience and significantly slow down iterative development, particularly in AI/ML environments where large shared datasets are hosted on platforms like VAST. To address this challenge, we recommend a workflow in which developers work remotely on local files and use background file synchronization tools to update the shared NFS directory. This approach offers a responsive local experience while ensuring compatibility with compute clusters accessing centralized data.

Common Applicable Scenarios

Remote developers use tools like Mutagen to asynchronously sync files from their local environment to a shared path (e.g., /mnt/vast) on GPU clients. These clients access data from the VAST platform over NFS. This sync-based approach ensures a responsive local development experience while maintaining centralized, shared access to data across GPU nodes.

ℹ️ Note

Note: The same flow can be used from a local file system on one of the GPU client nodes.

Local File Synchronization

Instead of working directly on the NFS mount, remote developers can edit files locally and use a synchronization tool to update the shared directory automatically in the background. This model significantly improves interactivity and reduces latency while ensuring that the compute cluster has access to updated files for job execution.

However, this approach comes with some limitations:

• Eventual Consistency: Updates are not instantaneous. Changes made locally may not appear in the shared folder immediately, which could affect time-sensitive workloads.

• Risk of Overwriting: Sync tools—especially in modes like "replica"—can overwrite files in the VAST-mounted directory. This is especially dangerous if multiple users access or modify the same files.

• Requires Sync Awareness: Developers must understand how and when sync occurs to avoid unintentionally pushing outdated files or losing changes.

• No Built-In Conflict Resolution: In most configurations, changes made directly on the NFS share can be overwritten by the local version unless special precautions are taken.

Example Tool: Mutagen

Overview

 Mutagen is a high-performance, developer-centric file synchronization tool designed for fast, continuous syncing between local and remote environments. Unlike one-time utilities like rsync, Mutagen runs persistently in the background. It is resilient to disconnections, making it well-suited for syncing with NFS-mounted storage during iterative development workflows. (Website: https://mutagen.io )

Mutagen operates entirely in user space and establishes a sync session between a local directory and a target directory (e.g., a locally mounted NFS path).

• Detects file changes in real time.

• Computes and transfers only file diffs.

• Automatically handles network interruptions and resumes sync.

• Supports both one-way and two-way sync with conflict resolution.

If the client machine mounts an NFS share locally (e.g., at /mnt/nfs-share), Mutagen can sync a local folder to that mounted path. See example setup below.

Note: This setup does not intelligently cache NFS. Instead, it creates a redundant copy of the data. Mutagen treats both directories as independent local paths and performs a sync between them. The NFS share must be mounted locally on the same machine running the Mutagen agent. Mutagen is not a transparent proxy or caching layer for NFS.

Example Setup

Step 1: Install Mutagen

brew tap mutagen-io/mutagen
brew install mutagen

Step 2: Prepare Local Folder

mkdir ~/project_local

Step 3: Create a Sync Session

mutagen sync create ~/project_local /mnt/vast/project 
#Assume the shared NFS mount is at /mnt/vast/project

Step 4: Monitor or Control Sync

mutagen sync list
mutagen sync monitor
mutagen sync flush     # Push all changes immediately

Advanced Sync Options

mutagen sync create \
  --name=vast-sync \
  --sync-mode=two-way-resolved \
  --watch-mode=portable \
  --ignore-vcs \
  ~/project_local /mnt/vast/project

Parameter Summary:

Common Sync Modes:

Summary

Accessing remote shared files over NFS may introduce delays that can slow development due to metadata round-trip and TCP overhead on small I/O. To improve responsiveness, remote developers can work on local files and use a tool like Mutagen to keep shared storage directories updated in the background. This model enhances developer productivity without disrupting the compute environment.

 Mutagen is lightweight, cross-platform, and highly effective in distributed development scenarios that involve large-scale NFS-based infrastructure like VAST.

That said, this approach introduces eventual consistency and potential overwrite risks and requires a clear understanding of how sync behavior works, especially when multiple users or automated jobs interact with the same data.