git-annex now has experimental support for tuning a repository for different work loads.

For example, a repository with a very large number of files in it may work better if git-annex uses some nonstandard hash format, for either the .git/annex/objects/ directory, or for the log files in the git-annex branch.

A repository can currently only be tuned when it is first created; this is done by passing -c name=value parameters to git annex init.

For example, this will make git-annex use only 1 level for hash directories in .git/annex/objects:

git -c annex.tune.objecthash1=true annex init

It's very important to keep in mind that this makes a nonstandard format git-annex repository. In general, this cannot safely be used with git-annex older than version 5.20150128. Older version of git-annex will not understand and will get confused and perhaps do bad things.

Also, it's not safe to merge two separate git repositories that have been tuned differently (or one tuned and the other one not). git-annex will prevent merging their git-annex branches together, but it cannot prevent git merge remote/master merging two branches, and the result will be ugly at best (git annex fix can fix up the mess somewhat).

Again, tuned repositories are an experimental feature; use with caution!

The following tuning parameters are available:

  • annex.tune.objecthash1=true
    Use just one level of hash directories in .git/annex/objects/, instead of the default two levels.

  • annex.tune.objecthashlower=true
    Make the hash directories in .git/annex/objects/ use all lower-case, instead of the default mixed-case.

  • annex.tune.branchhash1=true
    Use just one level of hash directories in the git-annex branch, instead of the default two levels.

Note that git-annex will automatically propagate these settings to .git/config for tuned repositories. You should never directly change these settings in .git/config, and should never set them in global gitconfig.