A single hdd can be fast enough to serve UHD ripped 4k video, but it’s much closer to the limit than an ssd would be, and might not be a great experience if you will be doing anything else with that drive at that time.

You might be mixing up your units here as 4k UHD is typically <90Mb/s while large HDDs typically cap out at 120MB/s, which equates to 960Mb/s (bits vs bytes). You could likely stream 10 4k UHD movies at once from a single HDD before running into bandwidth issues and with the cost of SSDs versus HDDs, it’s almost a no-brainer to go with an HDD.

And what would those “multiple reasons” be? Where is OP storing 400TB worth of downloads?

Yeah it only comes with 6 trays, so you’ll need to order more, but you can fill out the entire front section with drives.

I’m currently at 3TB a month and that’s with capping my seeding speeds to 2Mbps and remote streams to 3Mbps (essentially SD quality) to conserve what little upload speed I have to split amongst my users.

I don’t know why you’re so adamant that this can’t be the cause when video is hands down the most common reason for high data usage. Downloading a video is just 1x the file size in data usage but streaming to friends and family can easily increase that 1x infinitely based on the number of users. Then throw seeding on top of that and you increase it another 5x or what have you.

I’m browsing Tautulli right now and the little 4k content I have has a bitrate of 25Mbps for an hour long TV episode while movies like Akira in 4k has a bitrate of 90Mbps, Bladerunner 2049 70Mbps, Encanto 72Mbps. That crap adds up quickly. Imagine 6 kids who all have Encanto playing over and over again in the background, which amounts to 1TB of data used in 6 hours if they all play it 3 times.

What do you suspect is the cause of so much data usage if not video streaming?

I use a Fractal Design Define R6 but their newer model is around the same price (it actually appears to be $60 cheaper than the Silverstone case on NewEgg) and can hold the same number of drives. They’re solid cases.

https://www.fractal-design.com/products/cases/define/define-7/

For your lack of SATA ports, you can either buy a new mobo (use PCPartPicker and filter by SATA ports) or an LSI SAS HBA card to gain additional SATA ports.

Plenty of 4k HDR videos are 50+GB each and OP could have a dozen people or more watching each day plus new downloads, online backups, seeding, etc.

I have a decent sized server with terrible upload speeds in the 15Mbps range that I share with some friends and family, and I still have 5-6 people streaming from my server almost constantly. If I had a symmetrical connection, I wouldn’t be shy about sharing it more and uncapping the remote bitrate settings and I could easily see myself hitting these numbers even though almost all my content is 720p and 1080p.

Video is what gobbles up that much data. They likely have friends and family streaming from their media server.

It means you’re not human.

What if it executes and install Windows 11 on your machine!?