Therefore in short form.
You can install 4 hard drives with a capacity of 3TB and configure RAID in different combinations.
What else is important in my opinion is that you should set the network speed to Jumbo Frames 9000, when the station will be operated in a 1000 Mbit network and support all devices, including hub / switches this Jumbo 9000's. Thus, the copying speed in the network is by far better than in normal mode.
I think the large quantities of DSM-Mangers leaves virtually nothing to be desired or connection options open. There are an incredible number of Einstellmöglichekiten for all cases, but also explains very easy.
Unrestricted buy recommendation from me ...
Hope helps one or the other in his decision :)
But can I also ask because I now run 3 different Synology NAS on.