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I am about to setup my Raspberry Pi 2 as a plex server and wish to connect the old HDDs I have knocking around.

I want to use a powered hub as I know the Pi itself won't be able to power lots of HDDs. My idea is also that the hub powers the Pi itself via one USB port out of the hub and into the micro USB power port on the Pi.

I'm under the impression that the Pi 2 is safe being backfed, so that shouldn't be an issue, but my main concern is power.

I'm looking at two diff 7 port hubs,

http://www.modmypi.com/raspberry-pi/accessories/usb-hubs/pihut-7-port-raspberry-pi-usb-hub-eu-plug-5v-2a

And

http://www.amazon.co.uk/Anker-PowerIQ-Charging-Samsung-Motorola-7-Ports-3/dp/B00VE4UJD4#featureBulletsAndDetailBullets_secondary_view_div_1451262891516

one is known to work well, whereas I can find no comment about the anker one, (although from my experience, anker are one of the top manufacturers out there).

My concern is, will I be able to power up to 6 HDDs from the 2A hub (1 port will be used to power the Pi) or will I run out of power, and therefore should I pump out for the more powerful one?

I'm aware that the Pi 2 can't transmit at USB3 speeds, so that part will unfortunately be lost/wasted.

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  • shopping advice is explicitly off topic as per the sites FAQ raspberrypi.stackexchange.com/help/on-topic
    – Steve Robillard
    Dec 28, 2015 at 2:07
  • If you remove the shopping component and ask only about sufficient power I will reopen this question. Just ping me. Note that while powering the Pi from a USB hub ha been done and does work it is not recommended.
    – Steve Robillard
    Dec 28, 2015 at 2:14
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    This still doesn't look like a Pi question. You should be able to work it out yourself, but HDD typically use 500mA each. You do the maths.
    – Milliways
    Dec 28, 2015 at 4:13
  • @Robillard have you already edited it to take out the shopping çomponent? It looks like someone has! Whoever did, thankyou. Also, is it really not recommended? And by whom? I see so many articles/forum posts describing how to do it and very few saying that it shouldn't be done. I'm not saying you're wrong, I'm just saying that I've not seen much evidence of that being the recommended way.
    – Russ Wheeler
    Dec 28, 2015 at 9:45
  • Be really sure that your intended hub(s) are compatible before buying them. I've tried several USB 3.0 hubs with Pi's that did nothing.
    – goobering
    Jan 27, 2016 at 16:23

1 Answer 1

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I (sort of) disagree with Steve about powering the pi from a hub in the sense that it might be fine and I did it for almost two years without problems. The issue is that USB 2.0 power is supposed to be regulated to 500 mA. However, in reality it probably is not on most hubs, hence you can divide the total amperage of the supply between the ports.

Assuming the pi needs 1 A and each drive needs .75 A, that's 5.5 amps. I think it will be much easier if you use two smaller hubs with a 2+ A supply and power the pi separately. I.e., three plugs on a power bar.

You don't want sudden activity on a number of drives affecting the current to the pi.

The exact brand of hub should not matter much although you may want to search around and see if anyone says specifically it will not work. If feasible you might as well try a local retailer -- they will probably have a few suitable options and will take it back within N days, which makes things easier. As you are aware, you are also wasting your money by dishing out for USB 3.0, and note that attaching them via a hub's data cable will mean the total speed can be no better than attaching one drive (you might want to consider just spending the money on one bigger new drive).

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  • The benefit of the USB 3.0 hub is that it can give out up to 900mA on ask the ports and potentially 2.1A on one of them (apparently it detects the power needed somehow). That is one of my main reasons for getting it as it has 5A to spread across the ports instead of 2A on the utter one
    – Russ Wheeler
    Dec 28, 2015 at 16:43

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