I’m not saying that.
What you need to do is decide now if the drive you will buy will be used for a RAID array. If it is a desktop drive won’t be in a RAID array on a NAS system. Many NAS’ will have random writes to the pool. Desktop drives aggressively park the heads, the load and unload of the heads wears them. In a NAS system they can actually wear out.
Over the last 15 years drives have become a bit more specialized. You already found out about surveillance drives not being a good fit for much other than surveillance/DVR. Desktop drives are fine for desktop loads and usage but outside of that or single drive usage they are not useful. NAS drives are meant for NAS usage in RAID arrays. Back when the WD green drives were available years ago you could convert them from a desktop drive to a NAS drive using a tool called wdidle (WD Idle) but that isn’t the case any more.
Using a NAS drive on its own will work in a pinch but if it has an error it won’t try to recover it like a Desktop drive would because it’s made with the idea that it will be in an array that will deal with the issue. Plus once you start loading it up you will have to wipe it to put it into an array unless you go for ZFS mirrors or RAID 1. If the NAS Appliances have some sort of special trickery that allows you to expand one disk at a time and add redundancy I’m completely unaware as I’ve never put much stock in them. I’ve been running FreeNAS/TrueNAS for over 10 years.



I understand. If you buy a used server then add some drives later you can have a great NAS IMHO. I upgraded from an X8DT6-F with 384GB of RAM and a pair of Xeon X5690’s right before things went sideways. The MoBo has the SAS controller already flashed to IT mode so it’s ready for ZFS. But it’s not exactly light on power and with a 2U chassis and a handful of used 8TB SAS drives you are looking at around 1200.
My current server is a X10DRH-C with dual Xeon E5-2683 v3’s with 128GB of RAM in a 4U chassis with 11 X 8TB SAS drives in a RaidZ3 configuration. Just the MoBo, chassis, cpu’s and 64GB of ram is running about 1150. The drives used are 110 each and before you think you should just get those, SAS drives require a SAS controller and you only get those in enterprise equipment.
But if you can pick up a little here and a little there you can have a nice system. But right now isn’t a great time to get in the game.