rgd1101 :
To get that 900 MB/s you are look at professional system, it going to cost a lot too.
I only see ext 2 hdd raid, that might max out at 400 MB/s
They're gonna cost a lot but not as expensive as using SSD. I actually already have couple of option with the cheaper price for 20TB :
areca 8050T2 - 1100-1200MB/s at raid 6 (thunderbolt2) <-- my best option so far.
lacie 8 big - 1100MB/s (thunderbolt2)
lacie 6 big - can reach 1400MB/s at raid 0 (thunderbolt3) <-- this maybe the next option but has not got the fix price from local distributor.
areca 8050t2 enclosure only : $2100 + additional 8x seagate enterprise/constallation 3TB ($900) , so total about $3000+ which is till in my budget. I don't have know the price for lacie yet, i haven't got replied from them. So this areca is suppose to be enough for me. I assume they will be around under $4500.
The problem is that for this kind of speed , they still need to operate on thunderbolt port (no other option) ... and these drives (areca, lacie etc) still use previous thunderbolt 2 technology. Why is it the problem ?.... because i can't find any new mobo with thunderbolt2 support. For example if i want to use ryzen, the am4 mobo available on the market now does not support thunderbolt2. If using intel x99 mobo , only little option to choose and nowadays it's hard to find that thunderbolt2 card on the local market here. Thunderbolt 2 is not 'old' enough but every mobo fastly goes to usb 3.1 gen2 and thunderbolt3.
So i'm looking an alternative usb3.1 or thunderbolt3 raid system to be able to work with latest mobo model.