Just do not save your SWAP files on the External storage, else everything will be fine. as the open-e system SWAP files work as memory (related to the memory), so if you remove the External, and the system did not find the SWAP it may get crashed.

In another words, we do not suggest our users to install DSSv6 on the External storage, while using the external to save data, files etc, there is no issue about that.