There are two ways to reset your Synology NAS running DSM 7.0, including a soft and hard reset. Regardless of which method you use, your data will not be wiped, though it's highly recommended to make a backup of everything, just in case.
[h=2]How to reset your Synology NAS[/h][h=3]Soft reset[/h]The soft reset only clears the network settings and resets the admin password.
Full story from the WindowsCentral blog...