Like most multi device users I need to transfer files between my notebook and mobile devices every now and then. As I travel a lot, I have so far abstained from installing a file synchronization client on my PC or my mobile devices as I wasn't quite sure how to ensure that the synchronization process doesn't eat into my roaming data bucket. Also, I don't want my data traversing the data center of a commercial cloud storage provider for privacy reasons. My solution was therefore to transfer files via Bluetooth between devices when they are at close range to each other. For a file or two of a few megabytes such as a camera image that approach works quite well. But for larger files such as PDF documents with a size of tens and hundreds of megabytes or larger file connections, Bluetooth is just too small. And then there are mobile devices out there that can't send files via Bluetooth at all.
For these reasons I decided at some point to give Internet based file synchronization mobile apps a closer look. Since I have an Owncloud instance running on a Raspberry Pi at home that I already use for exchanging files between PCs, privacy and confidentiality was not an issue. Also, there are Owncloud file synchronization apps available for the major mobile platforms. So I went ahead and installed the Owncloud client on two mobile operating systems to play around with it. Usage is straight forward and the apps offer full control over which files are transferred (and when) and which files are kept in sync. File transfers work just as they should and while I'm at home, my DSL router recognizes that the public destination IP address is bound to the WAN interface and reflects the packets right back into the network without a hop on the outside. That makes file transfers as fast as my home Wi-Fi allows. When not at home, transfer speed is limited to the speeds I can get over the cellular network and the 25 Mbit/s downlink and 5 Mbit/s of my VDSL connection at home. That's still good enough for most file sizes.
Great stuff and one more reason to have my private Owncloud instance at home.