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 perhaps a backup
drive). 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: [[videos/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.
