Git LFS for large files - Deep Dive

Overview - Git LFS for large files

What is it?

Git LFS (Large File Storage) is an extension for Git that helps manage large files efficiently. Instead of storing big files directly in the Git repository, it stores pointers to these files, while the actual content is kept separately. This keeps the repository small and fast. It is especially useful for files like images, videos, or datasets that change often and are too big for normal Git.

Why it matters

Without Git LFS, large files make Git repositories slow and heavy, causing delays in cloning, pushing, and pulling. This can frustrate developers and waste storage space. Git LFS solves this by keeping the repository lightweight and speeding up operations, making teamwork smoother and saving bandwidth and disk space.

Where it fits

Before learning Git LFS, you should understand basic Git commands and concepts like commits, branches, and remotes. After mastering Git LFS, you can explore advanced Git workflows, continuous integration with large assets, and other Git extensions for collaboration.

Mental Model

Core Idea

Git LFS replaces large files in your Git repository with small pointers, storing the actual big files separately to keep your repo fast and light.

Think of it like...

Imagine a library catalog that lists books by their titles and locations instead of storing the entire book on the shelf. Git LFS is like that catalog, pointing to where the big books (files) are stored, so the shelf (repository) stays neat and easy to browse.

┌───────────────┐       ┌─────────────────────┐
│ Git Repo     │       │ Git LFS Storage      │
│ (small files │──────▶│ (large files stored  │
│  + pointers) │       │  separately)         │
└───────────────┘       └─────────────────────┘

Pointers in Git Repo link to actual large files in Git LFS Storage.

Build-Up - 7 Steps

1

Foundation

Understanding Git's file storage limits

Concept: Git stores all files and history inside the repository, which can slow down with large files.

Git keeps every version of every file inside its .git folder. When files are large, the repository size grows quickly, making cloning and operations slow. Git is designed for code and small text files, not big media files.

Result

Large files cause slow Git commands and large repository sizes.

Knowing Git's default storage helps understand why large files cause performance problems.

2

Foundation

What Git LFS does differently

Concept: Git LFS stores large files outside the main Git repository and replaces them with small pointer files inside Git.

When you add a large file with Git LFS, Git stores a tiny pointer file instead of the full content. The real file is uploaded to a separate server or storage. When you clone or pull, Git LFS downloads the actual large files automatically.

Result

Git repository stays small and fast, while large files are managed separately.

Separating large files from Git history keeps the repo efficient and manageable.

3

Intermediate

Installing and configuring Git LFS

🤔Before reading on: do you think Git LFS works automatically after installation or needs setup? Commit to your answer.

Concept: Git LFS requires installation and setup to track specific file types.

First, install Git LFS on your system. Then run 'git lfs install' to set up hooks. Next, tell Git LFS which files to track using 'git lfs track "*.psd"' for example. This creates a .gitattributes file that tells Git to use LFS for those files.

Result

Git LFS is ready to manage specified large files in your repo.

Understanding setup prevents confusion about why large files aren't tracked automatically.

4

Intermediate

Working with Git LFS tracked files

🤔Before reading on: when you add a tracked large file, does Git store the full file or a pointer in the repo? Commit to your answer.

Concept: Adding and committing tracked files stores pointers in Git and uploads large files to LFS storage.

When you add a file tracked by Git LFS, Git stores a small pointer file in the repo. The actual large file is uploaded to the LFS server when you push. When others clone or pull, Git LFS downloads the real files automatically.

Result

Repository size stays small; large files are handled behind the scenes.

Knowing this flow helps avoid confusion about file contents in the repo.

5

Intermediate

Cloning and fetching with Git LFS

Concept: Git LFS automatically downloads large files after cloning or fetching the repository.

When you clone a repo with Git LFS, Git downloads the small pointers first. Then Git LFS downloads the actual large files in the background. This keeps cloning fast and transparent. You can also fetch or pull large files separately if needed.

Result

You get the full project including large files without manual steps.

Understanding this automatic download clarifies how Git LFS integrates with Git commands.

6

Advanced

Managing storage and bandwidth with Git LFS

🤔Before reading on: do you think Git LFS stores all versions of large files forever or cleans old versions? Commit to your answer.

Concept: Git LFS stores versions of large files and may require cleanup to save space and bandwidth.

Git LFS keeps all versions of large files you push, which can consume storage and bandwidth. You can use commands like 'git lfs prune' to remove old unused files locally. On servers, policies may limit storage or require manual cleanup.

Result

Storage stays manageable and bandwidth usage is controlled.

Knowing storage management prevents unexpected disk space or bandwidth issues.

7

Expert

Handling Git LFS in CI/CD and collaboration

🤔Before reading on: do you think CI systems need special setup to handle Git LFS files? Commit to your answer.

Concept: Continuous integration and collaboration require Git LFS support to handle large files correctly.

CI/CD pipelines must install Git LFS and fetch large files to build or test projects properly. Collaborators need to have Git LFS installed to avoid broken files. Some hosting services provide built-in LFS support, but others require configuration. Understanding authentication and storage limits is critical for smooth workflows.

Result

Large files are correctly handled in automated builds and team environments.

Knowing integration details avoids build failures and collaboration issues with large files.

Under the Hood

Git LFS works by replacing large files in the Git repository with small pointer files that contain metadata and a unique identifier. The actual large files are stored on a separate LFS server or storage backend. When pushing, Git LFS uploads the large files to this storage. When pulling or cloning, Git LFS downloads the real files based on the pointers. Git hooks intercept Git commands to manage this process transparently.

Why designed this way?

Git was originally designed for source code, which is mostly small text files. Large binary files cause performance and storage issues. Git LFS was created to solve this by separating large file storage from Git's history, allowing Git to remain fast and efficient. Alternatives like Git submodules or external storage were less seamless or more complex, so Git LFS became the standard.

┌───────────────┐       ┌───────────────┐       ┌───────────────┐
│ Developer    │       │ Git Repository│       │ LFS Storage   │
│ adds large   │──────▶│ stores pointer│──────▶│ stores actual │
│ file         │       │ file only     │       │ large file    │
└───────────────┘       └───────────────┘       └───────────────┘

On clone/pull:
┌───────────────┐       ┌───────────────┐       ┌───────────────┐
│ Developer    │◀──────│ Git Repository│◀──────│ LFS Storage   │
│ gets pointer │       │ pointer file  │       │ actual file   │
│ and real file│       │              │       │ downloaded    │
└───────────────┘       └───────────────┘       └───────────────┘

Myth Busters - 4 Common Misconceptions

Quick: Does Git LFS store large files inside the Git repository itself? Commit yes or no.

Common Belief: Git LFS stores the full large files inside the Git repository just like normal Git files.

Reality: Git LFS stores only small pointer files inside the Git repository; the actual large files are stored separately.

Why it matters: Believing this causes confusion about repository size and leads to frustration when expecting smaller repo sizes.

Quick: Do you think Git LFS automatically tracks all large files without setup? Commit yes or no.

Common Belief: Git LFS automatically tracks all large files in the repository without any configuration.

Reality: You must explicitly tell Git LFS which file types to track using 'git lfs track'. It does not track files automatically.

Why it matters: Assuming automatic tracking leads to large files being committed normally, causing repo bloat and performance issues.

Quick: Does Git LFS remove old versions of large files automatically? Commit yes or no.

Common Belief: Git LFS automatically cleans up old versions of large files to save space.

Reality: Git LFS keeps all versions you push until you manually prune or the server enforces limits.

Why it matters: Not managing storage can cause disk space exhaustion and increased bandwidth costs.

Quick: Can you use Git LFS without installing it on your machine? Commit yes or no.

Common Belief: You can clone and work with Git LFS repositories without installing Git LFS on your system.

Reality: Git LFS must be installed locally to properly download and manage large files; otherwise, you get only pointer files.

Why it matters: Not installing Git LFS leads to broken or missing large files, causing build or runtime errors.

Expert Zone

1

Git LFS pointer files are plain text and can be inspected or edited, but modifying them breaks file integrity.

2

Git LFS uses Git hooks to intercept commands, so disabling hooks or using unsupported Git clients can cause issues.

3

Some Git hosting services impose bandwidth and storage limits on Git LFS usage, requiring careful management in large teams.

When NOT to use

Git LFS is not ideal for extremely large datasets that change frequently or require complex versioning; specialized data versioning tools like DVC or object storage solutions may be better. Also, if your team cannot install Git LFS or your hosting does not support it, alternatives like Git submodules or external file servers might be necessary.

Production Patterns

In production, teams use Git LFS with CI/CD pipelines that install Git LFS and fetch large files before builds. They track only necessary file types to minimize storage. Some use Git LFS with cloud storage backends for scalability. Teams also implement pruning policies and monitor usage to avoid hitting hosting limits.

Connections

Content Delivery Networks (CDNs)

Git LFS stores large files separately, similar to how CDNs store and deliver large media files outside the main website server.

Understanding Git LFS as a specialized storage and delivery system helps grasp how separation improves performance and scalability.

Database Indexing

Git LFS pointers act like indexes pointing to large data blobs stored elsewhere, similar to how database indexes point to data locations.

Knowing this connection clarifies how pointers optimize access without duplicating large data.

Library Catalog Systems

Git LFS pointers are like catalog entries that reference physical books stored in a warehouse, separating metadata from bulky content.

This cross-domain link shows how separating metadata and content is a common pattern for managing large collections efficiently.

Common Pitfalls

#1 Adding large files without tracking them with Git LFS.

Wrong approach:

git add big_video.mp4
git commit -m "Add video"

Correct approach:

git lfs track "*.mp4"
git add .gitattributes
git add big_video.mp4
git commit -m "Add video with LFS"

Root cause:

Not configuring Git LFS to track large file types causes Git to store full large files, bloating the repo.

#2 Cloning a Git LFS repo without Git LFS installed.

Wrong approach:

git clone https://example.com/repo.git
# No Git LFS installed

Correct approach:

git lfs install
git clone https://example.com/repo.git

Root cause:

Without Git LFS installed, only pointer files are downloaded, leaving large files missing.

#3 Ignoring storage and bandwidth limits of Git LFS hosting.

Wrong approach:

# Push many large files without monitoring
git push origin main

Correct approach:

# Monitor usage and prune old files
git lfs prune
git push origin main

Root cause:

Not managing Git LFS storage leads to unexpected costs and service interruptions.

Key Takeaways

Git LFS keeps your Git repository fast and small by storing large files outside the main repo and using pointers inside.

You must install Git LFS and configure which files to track; it does not work automatically.

Git LFS integrates transparently with Git commands but requires special handling in CI/CD and collaboration environments.

Managing storage and bandwidth is important to avoid running into hosting limits or excessive costs.

Understanding Git LFS's pointer system and separate storage helps you use it effectively and avoid common pitfalls.