There is a feature request to be able not to use a local cache at all,
only a network cache. With such a feature, the names "primary storage"
and "secondary storage" make less sense since ccache would be operating
in "secondary only" mode, but then that storage would of course become
the primary (and only).

Let's rename "primary storage" to "local storage" and "secondary
storage" to "remote storage" – operating in "remote only" mode then
makes sense.

One of the original motivations to call networked storage "secondary" is
that the file storage can be used for local file systems as well, making
such storage "not quite remote", but in practice I guess the file
storage backend used primarily for network file systems.