Happy Synology Custumer here, started out with 4 bay (3 x 4Tb drives in SHR), added further JBOD 4Tb drive for CCTV, upgrdaed original 3x4Tb drives to 3 x 16Tb Drive - using SHR upgrade was very easy, take one drive at a time out and put new drive in, NAS copied all required data automatically. Very impressed with how smooth the operation was.
Ive had the unit several years now, and it just sits in the corner, getting on with its job, combined with my main PC and cloud storage, I'm very happy that my data (for work) is in multiple places at once (One Drive, Main PC, and 2 x on the NAS) - seamless operation.