After you've used git-annex for a while, you will have data in your repository that you don't want to keep in the limited disk space of a laptop or a server, but that you don't want to entirely delete.
This is where git-annex's support for offline archive drives shines.
You can move old files to an archive drive, which can be kept offline if
it's not practical to keep it spinning. Better, you can move old files to
two or more archive drives, in case one of them later fails to spin up.
(One consideration when future proofing your archive.)
To set up an archive drive, you can take any removable drive, format it with a filesystem you'll be able to read some years later, and then follow the walkthrough to set up a repository on it that is a git remote of the repository in your computer you want to archive. In short:
cd /media/archive git clone ~/annex cd ~/annex git remote add archivedrive /media/archive/annex git annex sync archivedrive
Don't forget to tell git-annex this is an archive drive (or a backup drive; see preferred content.). Also, give the drive a description that matches something you write on its label, so you can find it later:
git annex group archivedrive archive git annex wanted archivedrive standard git annex describe archivedrive "my first archive drive (SATA)"
Or you can use the assistant to set up the drive for you.
(Nice video tutorial here: git-annex assistant archiving)
(Keeping the archive drive in an offsite location? Consider encrypting it! See fully encrypted git repositories with gcrypt.)
Then, when the archive drive is plugged in, you can easily copy files to it:
cd ~/annex git-annex copy --auto --to archivedrive
Or, if you're using the assistant, it will automatically notice when the drive gets plugged in and copy files that need to be archived.
When you want to get rid of the local file, leaving only the copy on the archive, you can just:
git annex drop file
The archive drive has to be plugged in for this to work, so git-annex can verify it still has the file. If you had configured git-annex to always store 2 copies, it will need 2 archive drives plugged in. You may find it useful to configure a trust setting for the drive to avoid needing to haul it out of storage to drop a file.
Now the really nice thing. When your archive drive gets filled up, you can simply remove it, store it somewhere safe, and replace it with a new drive, which can be mounted at the same location for simplicity. Set up the new drive the same way described above, and use it to archive even more files.
Finally, when you want to access one of the files you archived, you can just ask for it:
git annex get file
If necessary git-annex will tell you which archive drive you need to pull out of storage to get the file back. This is where the description you entered earlier comes in handy.