hmm

https://owncloud.org/faq/#rsync

"Why does ownCloud use csync rather than rsync?

rsync is a one-way syncing protocol. This means that if you have two servers and delete a file on one side, it will pop up again if you use rsync. To ensure old files get removed but new files added, and updated files overwritten, you need a N-to-N sync solution. ownCloud uses csync for syncing, which also deals with conflicts in a smart way."