usb drives with no phantom load

For a long time I've not had any network attached storage at home, because it's offgrid and power budget didn't allow it. But now I have 16 terabytes of network attached storage, that uses no power at all when it's not in use, and automatically spins up on demand.

I used a USB hub with per-port power control. But even with a USB drive's port powered down, there's a parasitic draw of around 3 watts per drive. Not a lot, but with 4 drives that's more power wasted than leaving a couple of ceiling lights on all the time. So I put all the equipment behind a relay too, so it can be fully powered down.

I'm using systemd for automounting the drives, and have it configured to power a drive's USB port on and off as needed using uhubctl. This was kind of tricky to work out how to do, but it works very well.

Here's the mount unit for a drive, media-joey-passport.mount:


That's on port 4 of the USB hub, the startech-hub-port-4.service unit file is this:

Description=Startech usb hub port 4
ExecStart=/usr/sbin/uhubctl -a on -p 4 ; /bin/sleep 20
ExecStop=/usr/sbin/uhubctl -a off -p 4

The combination of PartOf with Requires and After in these units makes systemd start the port 4 service before mounting the drive, and stop it after unmounting. This was the hardest part to work out.

The sleep 20 is a bit unfortunate, it seems that it can take a few seconds for the drive to power up enough for the kernel to see it, and so without that the mount can fail, leaving the drive powered on indefinitely. Seems there ought to be a way to declare an additional dependency and avoid needing that sleep? Update: See my comment below for a better way.

Finally, the automount unit for the drive, media-joey-passport.automount:

Description=Automount passport

The TimeoutIdleSec makes it unmount after around 5 minutes of not being used, and then its USB port gets powered off.

I decided to not automate the relay as part of the above, instead I typically turn it on for 5 hours or so, and use the storage whenever I want during that window. One advantage to that is cron jobs can't spin up the drives in the early morning hours.

censored Amazon review of Sandisk Ultra 32GB Micro SDHC Card

★ counterfeits in amazon pipeline

The 32 gb card I bought here at Amazon turned out to be fake. Within days I was getting read errors, even though the card was still mostly empty.

The logo is noticably blurry compared with a 32 gb card purchased elsewhere. Also, the color of the grey half of the card is subtly wrong, and the lettering is subtly wrong.

Amazon apparently has counterfiet stock in their pipeline, google "amazon counterfiet" for more.

You will not find this review on Sandisk Ultra 32GB Micro SDHC UHS-I Card with Adapter - 98MB/s U1 A1 - SDSQUAR-032G-GN6MA because it was rejected. As far as I can tell my review violates none of Amazon's posted guidelines. But it's specific about how to tell this card is counterfeit, and it mentions a real and ongoing issue that Amazon clearly wants to cover up.