Como artigo da wikipedia sobre Rackspace Cloud afirma, não existe uma maneira nativa de montar tal unidade virtual:
Caveats
There is no native operating system support for the Cloud Files API so it is not yet possible to "map" or "mount" it as a virtual drive without third-party software like JungleDisk that translates to a supported standard such as WebDAV. There are no concepts of "appending" or "locking" data within Cloud Files (which may affect some disk mirroring or backup solutions), nor support for permissions or transcoding. Data is organised into "containers" but it is not possible to create nested folders without a translation layer.
No entanto, o googling rápido revela projetos como Cloudfuse e MossoFS que criam soluções de montagem baseadas em fusíveis .