Repository Storage Types

Introduced in GitLab 10.0.

Legacy Storage

Legacy Storage is the storage behavior prior to version 10.0. For historical reasons, GitLab replicated the same mapping structure from the projects URLs:

Project's repository: #{namespace}/#{project_name}.git
Project's wiki: #{namespace}/#{project_name}.wiki.git

This structure made it simple to migrate from existing solutions to GitLab and easy for Administrators to find where the repository is stored.

On the other hand this has some drawbacks:

Storage location will concentrate huge amount of top-level namespaces. The impact can be reduced by the introduction of multiple storage paths.

Because backups are a snapshot of the same URL mapping, if you try to recover a very old backup, you need to verify whether any project has taken the place of an old removed or renamed project sharing the same URL. This means that mygroup/myproject from your backup may not be the same original project that is at that same URL today.

Any change in the URL will need to be reflected on disk (when groups / users or projects are renamed). This can add a lot of load in big installations, especially if using any type of network based filesystem.

For GitLab Geo in particular: Geo does work with legacy storage, but in some edge cases due to race conditions it can lead to errors when a project is renamed multiple times in short succession, or a project is deleted and recreated under the same name very quickly. We expect these race events to be rare, and we have not observed a race condition side-effect happening yet.

This pattern also exists in other objects stored in GitLab, like issue Attachments, GitLab Pages artifacts, Docker Containers for the integrated Registry, etc.

Hashed Storage

Warning: Hashed storage is in Beta. For the latest updates, check the associated issue and please report any problems you encounter.

Hashed Storage is the new storage behavior we are rolling out with 10.0. Instead of coupling project URL and the folder structure where the repository will be stored on disk, we are coupling a hash, based on the project's ID. This makes the folder structure immutable, and therefore eliminates any requirement to synchronize state from URLs to disk structure. This means that renaming a group, user, or project will cost only the database transaction, and will take effect immediately.

The hash also helps to spread the repositories more evenly on the disk, so the top-level directory will contain less folders than the total amount of top-level namespaces.

The hash format is based on the hexadecimal representation of SHA256: SHA256(project.id). The top-level folder uses the first 2 characters, followed by another folder with the next 2 characters. They are both stored in a special @hashed folder, to be able to co-exist with existing Legacy Storage projects:

# Project's repository:
"@hashed/#{hash[0..1]}/#{hash[2..3]}/#{hash}.git"

# Wiki's repository:
"@hashed/#{hash[0..1]}/#{hash[2..3]}/#{hash}.wiki.git"

How to migrate to Hashed Storage

In GitLab, go to Admin > Settings, find the Repository Storage section and select "Create new projects using hashed storage paths".

To migrate your existing projects to the new storage type, check the specific rake tasks.

Hashed Storage coverage

We are incrementally moving every storable object in GitLab to the Hashed Storage pattern. You can check the current coverage status below (and also see the issue).

Note that things stored in an S3 compatible endpoint will not have the downsides mentioned earlier, if they are not prefixed with #{namespace}/#{project_name}, which is true for CI Cache and LFS Objects.

Storable Object	Legacy Storage	Hashed Storage	S3 Compatible	GitLab Version
Repository	Yes	Yes	-	10.0
Attachments	Yes	Yes	-	10.2
Avatars	Yes	No	-	-
Pages	Yes	No	-	-
Docker Registry	Yes	No	-	-
CI Build Logs	No	No	-	-
CI Artifacts	No	No	Yes (Premium)	-
CI Cache	No	No	Yes	-
LFS Objects	Yes	No	Yes (Premium)	-