Sync software (like Seafile or Owncloud) for Windows and Android use

Question

I would like to set up some kind of backup and/or synchronization server on my network and I keep coming across Seafile, Owncloud, and a few other softwares that purport to be "Dropbox replacements". I haven't been able to sift through specs and reviews to find one that suits my particular needs, though they all seem to address most of them.

I am looking for a software that can

• Run on a Raspberry Pi (or Raspberry Pi 2 or -3)
• with a USB drive hooked up to it for storage
• support a small number of users (1 - 5). More is not bad
• support a relatively small number of devices (1 - 20). More is not bad.
• support file synchronization (ie Dropbox-like functionality) from Windows and android (more OS's are not bad)
• sync calendar
• sync contacts

Important technical considerations

• files must be encrypted locally before they hit the network (pre-Internet encryption)
• server administrators must not be able to arbitrarily and inherently decrypt another users files (users are responsible for their own keys)
• files, data, and preferably meta data must be stored in encrypted blob form
• no arbitrary limitations
• should work over a cell connection (for mobile devices)

Optional nice to have features

• support for standard disk encryption software like TruCrypt or alternative
• free

Answer 1

I'm using both Owncloud for my office and Seafile for my personal files. I started like you so I thought I'd try both for a while and see if I could make up my mind on which one to use for the long run.

Owncloud has a much cleaner, feature-rich cloud interface online, which is why I chose it for the office. Also, the community is larger and very active. So far I haven't run on a single problem that was not already documented online with clear steps to resolve it (I've been running Owncloud since v.6).

Seafile seems faster to sync large libraries. It's a robust platform and I can't find any feature I could complain about. That being said, the fine line between pro vs community editions seems less clear than for Owncloud and, the community seems to be mainly driven by a few core members coming from the for-profit side of the company. I am personally a bit concerned that this project will, at some point, become a 100% for profit.

With respect to encryption, Owncloud encrypts on the server and keeps the keys there. It has also be the source of 80% of my problems related to updates of the core (which are very frequently by the way) or to file sharing. Needless to say that I don't recommend it and, also see very limited value to it. I had to restart the install from scratch and reupload all the files to remove Owncloud's encryption at work. Once you activate it, you can't go back.

Seafile's encryption was done at the client's level but was flawed in its design from what I could read a year ago or so. However, Seafile may give you an extra level of confort in that it breaks up the files you upload into 'packets' kept independently of the file structure. This makes it harder for the system administrator to read your files on the server.

One last thought, Owncloud's sync client on Windows is much heavier on client's resources than is Seafile's.

Hope this helps your analysis.

Pierre