Haiperlink

I mostly need the photos when I'm travelling (mostly no internet connection). To prevent data loss I have a copy on my local NAS and for offsite copies my NAS and the NAS from 2 friends are synchronized.

Thanks for your answer GreatMarko. So the only possibility for me is to run sync only if the external harddrive is connected? Hopefully this will be fixed in the future, because I wanted to sync the photofolders between multiple NAS, but the main folder will always stay on my external harddrive..

I waited a long time for an unlimited sync service like BitTorrent Sync. I gave it a try to sync my photos from last year between 2 Windows 7 PCs with external harddrives (both in same network). The original folder ist 130GB and contains 25.000 Files. My external harddrive is not always connected on my main Notebook, so Sync shows that it can't open it. I'm pretty happy, that it recognizes the harddrive as soon as it is connected. The initial sync via WiFi took 3 days, which is ok for me, because it's just that first there was a break in between and it started to sync where it stopped. I had to stop the sync again just a few GB before the sync was complete. But when I connected the harddrive again this morning, on my second machine all files were moved into the .syncTrash folder and the synchronization started from the beginning. I'm pretty sure that there were no files changed on the main system.