Re: Dealing with slow USB disks, was: Re: Saving environment variables in u-boot

On Sun, Dec 19, 2021 at 10:03:47PM +1100, MJ wrote:
> 
> I would think a mechanical USB is going to pull a "lot" of power when beginning spin-up, but once rotating should be easily powered by a USB hub. Though this would not explain how it works on RPI4 unless the powered hub you're using is USB2.
> 

That's what I thought too. I certainly didn't expect the disk to work
without a powered hub. The Pi4 is a different animal; it has USB3 ports
and more power available. That the mechanical disk works at all on the 
Pi3's USB2 ports without assistance is quite surprising. 

There's a table at
https://hddfaqs.com/seagate-st1000lm048/
listing power requirements for the drive:
Required Power For Spinup: 1000 mA
Power Required (Seek): 1.7 W
Power Required (Idle): 1.6 W
Power Required (Standby): 0.18 W

So far I haven't tried to power cycle the combo, that might not work. 
Still, it's been an informative exercise. Getting rid of the hub is a
welcome simplification. The machine is still up after standing overnight.

Thanks for writing and motivating me to try the experiment!

bob prohaska

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