What is the difference between a USB hub and a USB port multiplier?

06
2014-04
  • Bigbio2002

    The diagram at this link is a bit confusing, I thought that only a USB hub was a device that existed.

    Edit: I know what the device is, and I was specifically looking for a device like it. It allows the connection of up to 16 drives through its two ports, via either a device called a "port multiplier", or from a hub through said port multiplier. What differentiates a USB port multiplier from a USB hub?

    • Answers
  • Jonathan Ben-Avraham

    The Addonics documentation leaves out some critical words that would clear up the situation. In their "Specifications" link they state:

    Maximum # of storage devices supported - 16 (requires combination of USB hubs or Port Multipliers)

    What they mean is:

    The maximum number of storage devices supported on the NAS 4.0's two eSATA/USB 2.0 combination connectors is 16. However, to use this number of stroage devices requires you to add either additional USB hubs or to use eSATAp port mulipliers.

    If you attach the storage devices to a USB hub, then they connect via the USB 2.0 feature of the combo connectors. If you use SATA port multipliers then the SATA devices connect via the eSATA feature of the combo connectors.

    Note that storage devices here can be either SATA or other types such as "disk on key". Any "disk on key" devices would connect via USB hubs. SATA devices could connect either through additional USB HUBs or through SATA port multipliers.

    The critical missing word before "port multiplier" in the Addonics documentation is "SATA". A SATA port multiplier allows you to attach multiple SATA devices to a single SATA host port, at the cost of some performance. See the Wikipedia article on SATA port multipliers.

  • AthomSfere

    It sounds like marketing to me. Perhaps that is there way saying its a powered hub. USB already has 127 devices per bus, so unless it adds a bus somehow...

    But, looking at your diagram, it appears it is way to setup NAS on USB devices through a single SATA / USB port on the NAS adapter. And because they are showing 5 drives, I would say it is powered too.


    • Related Question

    mac - MacBook USB-Hub
  • schneck

    I bought an active 7-port-USB-Hub to avoid all the cable mess on my desk. The following devices are plugged in:

    • Scanner (which is not being used, actually)
    • Keyboard
    • Mouse
    • Android-Phone

    When I now plug in a hard disk (passive, 2.5') as Time Machine device, it is not recognized. I wonder why this is the case, because it's an active hub. Do I really need to buy a hard disk with its own power supply?

    Another strange thing is, that when I plug the hard disk directly into the MacBook (beside the hub), it does not work either.


    • Related Answers
  • Arjan

    I believe the key here, is that he stated it's a passive 2.5" hard drive enclosure. That means that it may require two powered ports to have full power. The hard drive just may not be getting enough power.

    1. Is the hub plugged into a power outlet
    2. Does the usb cable have two ports? And are both being plugged into the usb hub?
    3. Does system Profiler see the drive?
    4. Does Disk Utility see the drive?
    5. What's the make & model of the USB Hub?
  • mouviciel

    Looks like the problem is not the hub but the disk.

    If it is visible from Disk Utility, try to format it with an HFS+ filesystem and a GUID partition table.

  • Arjan

    This does not explain why it won't work with the hub, but on the MacBook itself, all USB ports aren't created equal.