Annexed data is stored inside your git repository's .git/annex directory. Some special remotes can store annexed data elsewhere.

It's important that data not get lost by an ill-considered git-annex drop command. So, git-annex can be configured to try to keep a number of copies of a file's content available across all repositories.

By default, it keeps 1 copy; this is configured by running git-annex numcopies N, or can be overridden on a per-file-type basis by the annex.numcopies setting in .gitattributes files. The --numcopies switch allows temporarily using a different value.

When dropping content, git-annex checks with remotes to make sure If enough other repositories cannot be verified to have copies, it will refuse to drop it, avoid data loss.

In unusual situations, involving special remotes that do not support locking, and concurrent drops of the same content from multiple repositories, git-annex may violate the numcopies setting. It still guarantees at least 1 copy is preserved. This can be configured by running git-annex mincopies N or can be overridden on a per-file-type basis by the annex.mincopies setting in .gitattributes files. The --mincopies switch allows temporarily using a different value.

Note that [trusted repositories|trust]] are assumed to continue to contain content, so checking them is skipped. So dropping content from trusted repositories does risk numcopies and mincopies later being violated.

To express more detailed requirements about which repositories contain which content, see required content.

example

For example, consider three repositories: Server, Laptop, and USB. Both Server and USB have a copy of a file, and numcopies is 1. If on Laptop, you git-annex get $file, this will transfer it from either Server or USB (depending on which is available), and there are now 3 copies of the file.

Suppose you want to free up space on Laptop again, and you git-annex drop the file there. If USB is connected, or Server can be contacted, git-annex can check that it still has a copy of the file, and the content is removed from Laptop. But if USB is currently disconnected, and Server also cannot be contacted, it can't verify that it is safe to drop the file, and will refuse to do so.

With numcopies of 2, in order to drop the file content from Laptop, it would need access to both USB and Server.