Just chipping in here, in case anyone other than me is looking to connect a bunch of bus-powered USB 3.0 harddrives to a system.
I am looking to connect 10 4TB WD 2.5" harddrives to an older computer. The machine doesn't even have USB 3, so I have to add an expansion card as well, in the single available PCIe slot there is (this is an older Lenovo workstation with just two PICe slots).
I've actually spent quite some time on this, because adding ten bus-powered drives will draw quite a bit of bus power. I haven't been able to find specific data on the drives I've chosen (Western Digital WDBJRT0040BBK-WESN ("WD Elements SE")), so I looked for other 2.5" WD drives, and found the specs for this this WD Blue drive, which lists the power consumption in different operation modes.
Interestingly, the "spin-up" power draw isn't explicitly listed (as it is on the front of most, if not all, of my 3.5" desktop drives. But, a "peak" power draw is listed, which has to be the spin-up, because this is by far when drives draw the most power (like accelerating a car from 0 to target speed).
This peak power is listed as 1A at 5V +/- 10%. The other power values are listed in Watts, but this value is easily translated, as Watts are simply V*A, so the peak is 5W +/- 10%, i.e. 4.5~5.5W peak (or 0.9~1.1 Amps at 5V).
You can see that the peak power draw is much higher than any of the "operational" modes, or in other words, the modes while spinning, either "read/write" or "idle". You have to make sure you have hubs or I/O cards that can support the peaks, because this is the power that is drawn when you turn the system on, or bring a drive from standby/sleep to running.
Okay, so according to the WD Blue specs, if this drive were put in a USB HDD enclosure as-is, it would at peak draw more than the 1000 mA (1A) peak of the drive itself, because you also have to power the USB logic board, probably an LED, and account for a bit of power loss as well. That is, unless there's some firmware fiddling going on, such as letting the drive spin up slower so as to stay within the USB 3.0 specs. The USB 3.0 specs dictate a maximum of 0.9A of current to be drawn from any port.
Obviously, the drive in the enclosure I'm getting is not this WD Blue drive, but given its power specs which would exceed the USB 3.0 specs, I conclude that it would be foolish of me not to assume that no matter which bus-powered drive I attach, it may draw up to the max current allowed by the USB 3.0 specs, i.e. 0.9A, or 5*0.9=4.5W.
The first conclusion from this is that no hub without a dedicated power supply will suffice for more than one drive. And even with just one drive, a bus-powered hub might not be able to reliably power, say, a keyboard, mouse or USB stick while an HDD is spinning up using its power.
So, any bus-powered hub is off-limits to me.
But, worse than this, if you're really looking to plug a hub full of HDDs, you have to make sure the hubs are quite beefy, power-wise, and this disqualifies a surprisingly large amount of hubs out there, even some from reputable brands that are quite expensive.
E.g., if you buy a 7-port hub, you would need one that can provide 7*0.9A of current at 5V, or 6.3A (31.5W). I dare you to find one (at anything resembling a reasonable price). The interwebs is ripe with bad USB hubs. I want something price-effective as well, so I initially went searching on AliExpress, but man, even if they look like they're good (e.g. Orico), and their reviews are great (on AliExpress, where I think the reviews are generally unreliable, skewed towards too-positive, due to the way their reward system is (was, they kinda fixed this) set up), when you start to search the greater webs and find them on, say, Amazon, you get to see the really really bad reviews.
So, I abandoned the cheap cheap options, and looked at getting something cheap, but from a brand I personally know not to disappoint. From the local retailers in Denmark, DeLock and LogiLink are brands that I think aren't really "brands" as such, but pickers of cheap hardware where they have a proper QA resulting in reliable hardware.
For the PCIe USB 3.0 adapter, I've chosen the cheap LogiLink PC0057A card, which states that it will deliver the USB 3.0-specified 0.9A per port, if I read the text correctly. And even if I don't, as you'll see, I'll use the power on only two ports, so chances are it'll work, especially given the fact that it takes a Molex connector for providing extra power.
It uses the VIA VL805 chipset, which AFAICT works out-of-the-box in Windows, Linux, and macOS, and I'm building a Hackintosh, so this is important to me. It also appears to be a chipset used by motherboard vendors, so my expectation is that it is reliable.
For the hubs, I've chosen two LogiLink UA0170 4-port hubs. I found also a nice 8-port LogiLink hub in aluminum and all that, but its power adapter delivers 2A at 12V, so 24W, or 3W per port max (assuming its power distribution is properly designed (it has a "fast-charge port")), or 0.6A, which is not enough to support every port simultaneously drawing max power, and ALSO NOT ENOUGH TO COMPLY TO SPECS, SO WTF :D.
The 4-port hubs I've chosen, though, come with 5V 3.5A PSUs, which still don't supply quite enough power — we need 0.9*4=3.6A, but it is darned close, so I'm banking on either luck here, or good capacitors in the hubs.
Good thing here is, I have four ports on the PCIe card, two of them will power and connect the first two drives, the last two ports will go to the hubs which will power and connect the last eight drives.
But, even if it turns out that the two hubs with their 3.5A on paper start complaining when I draw 3.6A of 5V goodness, I can still add a third 4-port hub and then put three drives on each of the now three hubs, the 10th drive on the last usb port on the card itself, leaving three ports open, one on each of the hubs, for other stuff.
Note that I haven't actually received any of this stuff yet, I've just finally ordered it, so I'm only talking from investigation, not actual experience :)
I will update this with my actual experience if I remember it. If I forget and you want it, comment and I'll remember :D
UPDATE: The PCIe card that I ordered was absolute crap. The internal Molex connector came soldered on at a tilted angle, protruding from the PCB. I removed it and attached a Molex cable instead. Then, the actual stability proved to be absolutely horrendous. Restarts would leave it not recognizing the devices attached to it, and you'd have to plug and unplug cables for five, ten or more minutes for it to finally register everything. Terrible. I finally gave up on it, and switched to a laptop with USB-C ports which I bought Ugreen USB 3.0 hubs for, and everything worked fine. Also worked fine on a 2014 Mac mini with 4 USB 3.0 ports on the back.
The hubs are so-so. After about a week, one PSU died. I got a replacement, on now, several months in, the remaining two PSUs are still humming along, having no problem driving four drives each.
