git-annex can be configured to require more than one copy of a file exists, as a simple backup for your data. This is controlled by the "annex.numcopies" setting, which defaults to 1 copy. Let's change that to require 2 copies, and send a copy of every file to a USB drive.

# echo "* annex.numcopies=2" >> .gitattributes
# git annex copy . --to usbdrive

Now when we try to git annex drop a file, it will verify that it knows of 2 other repositories that have a copy before removing its content from the current repository.

You can also vary the number of copies needed, depending on the file name. So, if you want 3 copies of all your flac files, but only 1 copy of oggs:

# echo "*.ogg annex.numcopies=1" >> .gitattributes
# echo "*.flac annex.numcopies=3" >> .gitattributes

Or, you might want to make a directory for important stuff, and configure it so anything put in there is backed up more thoroughly:

# mkdir important_stuff
# echo "* annex.numcopies=3" > important_stuff/.gitattributes

For more details about the numcopies setting, see copies.