Just a short reminder course for me, doesn't uncompressed bt.601 require 27 megabytes a second. (OK, I realize a tad less due to missing video data during blanking period, let's approximate this extra data as the parity bits). If the device had a custom method to spread out the data across 20 controllers we are talking 1.3 megabytes/sec per controller. I'll assume the drives read and write in almost straight lines. Your drives all need to be media grade still, all it takes is a thermal calibration cycle, and the video record/playback will be messed up.
I'm assuming this server, or the device it's attached to has at least a few frames of cache buffer ram.
I would guess that each drive would need to burst 2mb/sec when reading or writing, and sustain 1.3mb/sec. In straight lines without a file system, on an SD card, this may be possible depending on the SD card's controller.
I know, if writing non-stop to high density high speed m.2 flash drives, they do heat up and throttle down, but, the fact that all these flashes are isolated chips on separate boards, each running slow, they might save you thermal problems here.
I think you are sitting on the border with the Amiga device, but, in the coments, user's say it works on SCSI-I buss as well as SCSI-II and this one is a shit load faster with 10mb/sec, worst case 5.5mb/sec support:
http://amigakit.amiga.store/catalog/product_info.php?products_id=1314 Though, it costs more, you now have huge safety margin.
Here is the board you selected, but used in a PC environment instead of an Amiga.
The video claims 1mb/sec, though, this may be a bottleneck of the PC.
Many others have used this device in a PC, MAC, NeXT, Roland digital synths/sound mixers, and of course Amigas. It seems compatibility wont be a problem, it's will the throughput be good enough.
The array is used to record and playback uncompressed bt.601 video.
If your array did any minimal lossless signal compression at all, like a 1.5:1, or 2:1, or 1.25:1 (4:2:0 video) then, these SCSI2SD devices would clear your speed hurdles instead of going right to the edge of just making it.