#Tech question:
I have two #USB 3 slots on my computer, but it seems like they cannot perform I/O operations simultaneously, e.g. moving files from one connected flashdrive to the other, whilst it is no problem to do so from a device connected to one of the USB 2 slots to one connected to a USB 3 slot.
Is this normal behaviour, is it a #Linux issue or is it just my computer?
Note: I can connect 2 devices to the USB 3 ports, use them after the other, without disconnecting one.
This is most likely an issue with your USB controller
Both ports share bandwidth and one overwhelms the other 
@mina Years back I copied directory trees from one external USB disk to another without that problem. It was USB 3 already, probably 2018/19, B.C, (before Covid). The OS was Ubuntu, most likely 16/04 LTS.
Your experience sounds odd, and I don't think it is a Linux problem.
To rule it out, you could run the computer from a FreeBSD USB stick (getting from https://www.freebsd.org ) and see what happens.
@mina
It should be the other way around. After initializing the transfer from the CPU the transfer itself should run directly from one device to the other without any CPU or main RAM involvement. After all the “B” in USB means “bus”.
@mina Oh, there could be a problem if one of the storage devices does not announce itself correctly on the bus and expects to talk to some master (the CPU). So it may be worth to check this with other storage devices.
@mina
Das mit dem wifi Adapter kann auch ein Problem mit dem USB 3.0 Standard sein, welches das Wifi Signal Stört. Die Geräte sollten deshalb relativ weit entfernt voneinander ans Mainboard verbunden werden. Evtl über eine Verlängerung, mit nicht zu dünnen Kabeln lösen.
Ansonsten gibt es gerne mal Probleme mit Datei Übertragungen je nach Linux Betriebssystem.
Ein Windows (To Go) zu booten wäre da eine praktische Fehleranalyse. Tritt der Fehler dort nicht auf, dann ist es kein Hardware Fehler oder Bandbreiten Problematik.
Wenn es nicht zu kompliziert ist, könntest du auch bezüglich beider Probleme im BIOS deine USB ports vielleicht auf USB 2.0 speed stellen. Das würde die Interferenz Problematik mit dem wifi und Software Probleme mit USB 3.0 unter Linux klären.
@mina this is not normal under any operating system.
Slowdowns yes, completely stalling out, no.
That said, if the combined peak power draw of both devices exceeds what the root hub can deliver, then only one of the two devices can be active at a time. If you have a powered USB hub to spare, put it between the second port, and the second device. If things start working as desired, the root hub is underpowered.
Some keyboards have a USB slot - probably at the rear.
@mina@berlin.social
To me this sounds like the two USB3 slots connect to only one adapter chip. Data is copied from drive A to memory and then back from memory to drive B. Old-ish computer?
@mina USB is organized in HUBS. So if the 2 USB 3.0 are on the same HUB, they share bandwith (and maybe even power?).
Not an expert. But that's my idea of where the problem could originate.
@mina interesting. Never heard of something like that. What errors do you get moving the files? And is it only moving of can't you copy them as well?