Hi, just set up the openmediavault software on my raspberry pi 3 and added 2 hdd's and using my local network everything's perfect. But I also want to access my cloud when I'm not at home, using a mobile app or via the web. Is that possible? Thanks.
I agree with the master. There are a number of ways to do this ranging from simple/easy to advanced - depending on your needs.
I helped someone a few months ago - see post below - that explained how to get FTP and/or VPN working.
I have heard that you can also use webDAV - there is a plugin for this -and it works like FTP but is really easy to setup as I don't think you need to do port forwarding.
If you really want something advanced with similar functionality to dropbox, then there is NextCloud. There is a really good Q and A for getting this setup.
I personally use VPN as it has good balance of security and utility. It gives me full access to my RPI when away from home. Also allows me to watch all my TV services Sky/Netflix etc when overseas on holiday.
Happy to help with VPN/FTP and suggest you start with easy/simple solution and then try more complex stuff.