Hello, I use a Synology 2 bay (212+). Love it. works across windows, MAC and my samsung note (whatever OS it uses?). I transfer pictures from my camera and they transfer to my laptop and desktop PCs automatically. I never had an issue with the sync function. I am now in Saudi with full remote access of my Synology (based in Ireland) available to me. Works just like dropbox. I rarely have an issue with remote access and just sycned a load of photos that my wife has taken.
Synology have a big range of stuff, I chose the 212 model (i think now it is the 213 version) as the better models have more processing power and larger RAM. I have mine set on Raid setup (2 x 3TB drives). A few times a year I have a couple of older hard-drives that I use to do a full back-up and store these at an external location (in case of fire/flood etc).
The great thing about the Synology is that it is very customisable and great for so many differnt devices - even for streaming music /video around the house. Best of all, I waste barely no time as I dont have to sit at my PC manually having to copy files here and there. For extra piece of mind, the sync function works by coping files I add (as example) from my camera to my desktop PC via the Synology to my other devices such as my laptop. Hence I have here 3 seperate locations of my files (PC, synology, laptop) excluding my old hard-disks that I have stored at an external location.
I did consider other devices such as from Western Digital etc, but online reviews put me off - too many issues. Synology always seemed to get better reviews.
Canon 80D, 700D & G7 X; EF-S 10-18/18-135 STM, EF-S 18-135 IS USM, 50 F1.4, 100 F2.8L Macro, 16-35 F4L, 70-200 F4L IS; 100-400 L II, Speedlite 430EX II