Since you mention file system, what FS would be optimal going forward for the USB connected drives? I use windoze primarily but do occasionally use some Linux variant. I want to be able to read and access backups outside of NAS in the event it fails - it is not exactly new! I have used several applications in windoze to access ext(x) drives and am comfortable doing that.
I am going to be relegating this nas to backup duty soon and am just beginning a backup regimen. Once all is set up on the new nas the old one is going to see some changes. I want to use it for automatic backups of our most critical data. I am not clear just yet how but basically I want the old backup nas to be shut down most of the time, wake up on schedule, backup the necessary data, time sync, send some reports and go back to sleep. On a separate track I will do a weekly backup of the new nas - again changed files only via external usb drive dock.
Since Qnap has ended firmware support I am considering converting my old box to full blown Linux but that creates another can of worms I would rather not deal with. However, this may be the simplest way to have the internal drives of the nas write the files in a way they can be read on an external system when the box finally dies.
I just started using a FIDECO Hard Drive Docking Station https://www.amazon.com/gp/product/B075ZJVZ42/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1
and it seems to be working fine. I haven't fully tested it but one slot seems fast and works with the first 4T drive I dropped in. The drives I am switching to are WD40EFRX Western digital red 4T units. but most of them will be in the NAS raid array. The drives that will be doing backup duty will be the old WD red 2T drives coming out of active service. Since these drives will be out of the system in an esd protective bag /case most of the time and data will be verified after writing, this should do for now.