I had seen several threads in various forums about people jonesing over hard drive space, especially because of how big msfs 2020 is becoming. So here are some suggestions for black friday!
Just be careful with Reds for a couple reasons:
The firmware is designed for RAID, and as a result will intentionally fail early on reading bad sectors to allow another disk in the array to take over - if you use one of these solo and it starts to go bad, you get less opportunity to save the data than a regular consumer disk that will continue to retry (while the system shows no progress, it is trying) reading the bad sector.
WD got caught out selling some models as SMR (shingled recording) which are much slower on random writes, which may or may not be your use case. Avoid regular WD Reds - but the shown Red Plus or the Red Pros if those are more your flavor, are CMR (conventional) and fine.
I have been using WD Reds (CMR models, before they were rebranded as “Plus” as a 4TB Raid1 for years without issue. I also recently added a Raid1 pair of 3TB plus models, that work great.
If you have a Red “regular” SMR drive, don’t mix it with a CMR disk in RAID unless you want funky disk performance issues. Ask me how I know!