External USB Hub appears to result in USB devices dropping out

[kernull]

Is anyone using a external USB hub just to have more devices plugged in for passthrough? Is this type of setup not recommended? I ask because it seems like im losing devices randomly from the guest perspective. I suspected issues with this USB hub itself and had replaced it thinking maybe it was bad... but the problem persists.

if anyone is using an external usb 3 hub, please let me know make.model!

thanks

 

[leesteken]

If you're doing USB passthrough then using hubs does not increase the number of devices you can passthrough (officially 5) because you have to passthrough each port/device connected to the hub separately.
Are you doing PCI passthrough of a USB controller? Then hubs should just work, unless the motherboard does not provide enough power or the port does not have enough bandwidth. I would suggest trying a powered USB hub. How many devices/hubs are we talking about and what kind (as they all need power and bandwidth)?
(My motherboard has only one USB controller on-board and uses multiple internal hubs to provide more USB 3.0 and 2.0 ports, and they appear to work fine, but that does not help you.)

 

[kernull]

hey leesteken!

If you're doing USB passthrough then using hubs does not increase the number of devices you can passthrough (officially 5) because you have to passthrough each port/device connected to the hub separately.

i didnt know about the 5 max per VM, but in these cases, im only looking to hookup some external USB devices including some hard drives (these are actually temporary) and also my cyberpower UPS (just started playing with NUT monitoring for this UPS) to individual VMs.

I'm not trying to passthrough the whole hub, just multiple devices on the hub to multiple VMs.

I am using an Anker powered USB 3 hub, and the hard drives are WD that are powered by the USB port as well.

I had unplugged things from te hub and plugged them directly into the mobo to confirm this is a external hub problem and I did notice that the NUT service seemed to somehow lose comms with the UPS even though it was still listed in lsusb... I restarted the nut-server service and it seems to find it right away again... then lose it after a minute so that might exclude the UPS from this issue... I'll hafta look into this.

The USB hard drives (currently plugged into mobo directly)
have not disappeared yet.

thanks!

 

[leesteken]

Sometimes enabling USB 3.0 (usb3=1) even for USB 2.0 ports or devices helps. USB passthrough to VMs has a lot of CPU overhead and is not well suited for low latency or high bandwidth devices (like drives or TV tuners). Even a USB keyboard (connected via a USB hub KVM) can sometimes miss a key press or release. Maybe the devices also notice a less than perfect connection and disconnect from their end?