Stress testing a Pi...

Well it was always going to be a shot in the dark...:-)
And I think I can confirm that a Pi4 cannot drive three SSDs over USB unaided.
As soon as I tried to rsync a new drive as a backup, via NFS, I started to get disk errors. On unrelated disks...not involved in the transfer.
The PI4 had a TV card on it that gets pretty hot so I removed that to reduce load on the power supply, but significantly it made *no difference at all*.
I hooked up a n HDMI screen to monitor the console messages and it was full of disk errors of one sort or another.
Not necessarily related to the drive in use.
My tentative conclusion, which I would like some opinion on, is that it is the USB power limit that is causing the problems, not the overall power draw. As that would have bee relieved by removing the TV hat.
Now as far as I can tell the total USB power available on the PI4 equates to 1200mA.
But on the Pi 5 that increase to 1600mA, provided you tell the board it has a 'high power supply'.
I believe there is a config.txt option to do  that. Even if you don't have the 'approved' PSU.
So I am thinking of going to a PI 5 rather than a separately powered USB adapters for the drives - the other way to  increase power to the drives.
Or is there a better one board computer alternative?
I want to build everything into a small 19" case with an ethernet switch   board and OSUs to reduce clutter
--
Of what good are dead warriors? … Warriors are those who desire battle more than peace. Those who seek battle despite peace. Those who thump their spears on the ground and talk of honor. Those who leap high the battle dance and dream of glory … The good of dead warriors, Mother, is that they are dead.
Sheri S Tepper: The Awakeners.