Currently running 8 HDD's on one machine and 6 on the other for right now. I could fit another drive cage on the "big rig" I suppose but I'm well over 50TB on it now. I'm mostly leaning toward 10TB NAS drives right now when I can...which is not often. I've had good luck with Seagate NAS drives and if they are in warranty they say free data recovery if they crash.
I don't buy into the WD are better than Seagate drives btw. (couple posts above.) RecentlyI stated I had a Toshiba NAS drive fail early, but after checking it actually was an HGST 4TB NAS drive.
They all become boat anchors in the end.
But I thought you were preserving your retirement money?
One of the issues with running so many drives inside a case is heat and power consumption. And here in Calimexistan our power is extremely expensive as well, so using less power is a HUGE plus.
Putting them off the case in a separate enclosure like the Mediasonics and enabling power management cuts down the heat, vibration and power, all of which extend the lives of your drives (SSDs too).
The 10TB NAS drives are very pricey still. With a Mediasonic case and four 6TB drives in a RAID5 you'll get a reliable 18TB of storage. If you wish to spend money, though, 4 10TB drives will give you 30TB. But I haven't seen any used 10TB NAS drives yet.
Mostly, buying lots of used network drives works because they tend to come from a corporate user that is upgrading and tend to be time and design coherent devices... plus they have common use lives. It turns out those are the highest quality drives you can buy used, they are not being sold because they have problems but because they are being replaced with larger displacement drives...
I've been buying WDC drives for quite a few years now. I guess it's what you get used to. I do have some very old Seagate PATA drives in the Ubuntu Apache server... and those have been running for close to 18 years now.
BTW, How the hell did an HGST NAS drive fail? Those are, in my experience, some of the best in the market!