Subj : Re: Stress testing a Pi...
To   : The Natural Philosopher
From : Pancho
Date : Sat May 11 2024 17:22:30

On 11/05/2024 09:53, The Natural Philosopher wrote:
> 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'.
>

1600mA isn't that much more than 1200mA. There is quite a difference in
the power requirements of different SSDs. Kingston A400 drives have a
max wattage of about 1.5 watts. Some other SSD drives quote up to 5
watts. NVME drives even more.

So If I were you, I would want to understand the drives you have, know
their power consumption, before making a decision.

FWIW, I only have one USB SSD running off an unpowered cable. The
additional drives use a secondary power supply, but I use spinning HDDs
as well as SSDs, so I needed to.

Also, the Pi 5 is a great computer, so worth buying just for fun. You'll
find something to use it for.

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