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git-fastcdc

Split certain files using content-defined-chunking for faster deduplication. It has a similar use-case to git-lfs, but blobs are in-repository. git-fastcdc mitigates some of the speed penalties. For most use-cases you are probably better off with git-lfs. If you have a focus on archival and deduplication, git- fastcdc might right for you.

Enable

git fastcdc install

Config

Edit .gitattributes:

*.wav binary filter=git_fastcdc
/.gitattributes text -binary -filter
/.gitignore text -binary -filter

By default git-fastcdc runs in-memory. Switch to on-disk:

git config --local fastcdc.ondisk true

If you have a pure git-fastcdc repository, you probably want to disable delta-compression to benefit from the speedups through fastcdc.

git fastcdc delta disable

Which will set core.bigFileThreshold to 200k which isn't exect science. It means most of the history- and meta-data is delta-compressed while most of the cdc-blobs aren't.

Results

For my repository - 800GB of music collection:

  • Without git-fastcdc delta-compression took over 5 hours (actually it took all night)
  • With git-fastcdc delta-compression takes about 2 minutes
  • With git-fastcdc the repostiory got slightly smaller: about 1%

So much faster repack, with the same delta-compression.

Methodology: I took one state of my repostory from 2 years ago and one state from today. A lot of meta-data has changed in those two states, because I am constantly fixing these using beaTunes. In both tests I created two commits and did reapck -a -d -f at the end.

How

It will split files on filtering when you add them. The split files go into the git-fastcdc branch. You need to push this branch to remotes too!

You will see the actual data in the files in the working copy, in *.wav in the example above. But actually the blobs of these files are just a list of chunks.

Repository Status: Personal

This repository hosts a project that is actively maintained but primarily intended for my personal use. It is public for transparency, sharing ideas, and as a resource for others who might find the methodologies or implementations useful. Please consider the following:

  • Status change: Should there be significant interest in this project, I am open to changing its status to accommodate broader collaboration and development.
  • Personal Project: This is a personal project, and while it is actively maintained, it is tailored to my specific needs and use cases.
  • Limited Support: Given the personal nature of this project, support and responses to issues or pull requests might be limited. I encourage open collaboration but may prioritize changes that align with my personal use.
  • Viewing and Forking Encouraged: You are welcome to view, fork, or use the code in your own projects. However, this project is provided as-is, with no guarantees of regular updates or adaptations for broader use.
  • Contribution Guidelines: While contributions are appreciated, they should be relevant and beneficial to the project’s ongoing development. Please review any provided contribution guidelines before making pull requests.

Feel free to explore the code, and utilize it under the terms of the license attached to this repository!