Please note: OwnCloud SERVER software should not be installed on Macs - you must either run it on a Windows or Linux machine. OwnCloud has seriously flawed code relating to the way it deals with file name encodings - it does not follow recommended practices - and the code falls apart on the Mac. Although the Mac community has repeatedly offered time and resources - test machines, programming, etc. - since version 6, the developers have not shown sufficient interest in fixing the needed bugs, officially (some users have already provided bug fixes, but these remain untested and unverified by the developers, and the Mac continues to be an unsupported platform for the Server).
As a consequence, if your OwnCould Server is a Windows/Linux machine, your OwnClient Client will function nicely. If your OwnCloud Server is a Mac, and you have a mixture of clients (Win/Mac/Linux) accessing your Server, you *will* lose files.
OwnCloud has a nice interface, and nice features, but until the developers take up the offers in the community to implement *proper* Mac support for both client AND SERVER, Mac users should proceed with caution.