I would not make the same choices today: I got a somewhat high end one and upgraded it to whopping 32GB of RAM, thinking I'd use it for running lightweight containers or VMs, and maybe a media server. But once I put all my data on it... including 20 years of family photos and tax prep documents and work stuff and everything else... I changed my mind and am using it only and solely as an internal storage unit. Basically, as mentioned, committed to the "NAS" as opposed to "Fun Project" path :-). So I could've saved myself some money by getting a simpler unit and not upgrading it. (the DS918+ also can hook up to a cage [DX517], but I ended up not needing that either, yet).

I have it with 4 WD Red Plus NAS 8TTB drives and RAID 10 currently. I've used RAID 5 in the past but decided against it for this usage - again, went for simplicity.

Just shy of 30,000 hours on the drives, daily usage (I basically don't use local drive for any data on any of my computers; I keep it all on NAS and this way I can use any of my computers to do/access the same thing), and really no issues whatsoever so far.