Would it be worth it use drive spin-down in order to save power?
You would likely end up losing out in responses to both upload and download requests if your disk ends up spinning down. So you would save power but you would also not make as much income. There have been some people on here with significantly lower success rates due to using USB drives which would possibly be about the same in terms of response as a spun down HDD.
Also HDDs die earlier if you let them spin down/up all the time. It is the most healthiest way to let them spin 24/7. They don’t consume that much power to make the power savings worth the HDD dying earlier.
And since storagenode will still read the HDD every couple minutes the savings would be quite small anyway.
Activity is constant enough that it won’t spin down anyway.
Even unvetted nodes receive requests at least once every minute (in my experience) so it doesn’t make sense to spin down the disks