Is there a limit to how many external drives can be connect to MBP

[victoreric]

I have a 2021 MBP and have 6 external harddrives that I connect through 2 usb hubs. I am only able to see only 4 of these harddrives at any one time and I'm not sure why. I have a usb-a hub and a usb-c hub. The MBP only has usb-c connection so I have the usb-a hub go into one of the usb-a ports of the usb-c hub, which then connects into my MBP through the usb-c connection. I'm not sure if this may be a factor.

 

[Raz0rEdge]

USB has a 255 device limit on each of it's buses. You are well within that, so you should be able to see all 6 drives as long as they are sufficiently powered.

If there is a limit, it might be on the hub side as opposed to the MBP.

 

[Slydude]

Are these drives drawing power from the USB or from their own power supplies? As I understand it the USB C hub is connected to your Mac with the USB A hub connected to that hub. The drives are then connected to that USB hub.

Here's what I think is happening. USB A hub is only ab le to draw a certain amount of power from the port that it is attached to. That power is then divided among the various drives leaving some of them without power.

How many USB C are there on your hub? If you have uncut USB C ports I'd get several UsB C to USB female adapters. Plug those into the USB C ports and then plug the drives into the adapters. This eliminates the second hub.

 

[victoreric]

I have 3 solid state drives that draw power from the hub and 3 regular HDs that have their own power source. There are 4 usb-a ports on each of the hubs and they but have their own power source. The drives which aren't seen by the MBP are both the SSD and the HD (with their own power source). Also, when I touch the unrecognized drives, there seems to be power to it because I feel it running. So I'm not sure if it's a power issue.

I will try to get an adapter and plug the usb-a hub directly into the MBP usb-c and see if that eliminates the problem.