Is there a limit on the number of USB external drives?

Is there a limit on the number of USB external drives?

I've got three external HDDs, all My Books, 500 GB, 750 GB, and 1 TB. If I hook one or two of them up to a computer, everything seems fine. If I hook all three of them to a computer (I've tried this on two different computers, one running Windows XP, one running Windows Vista), the bootup time goes up by more than an order of magnitude. It can suddenly take about 10-20 minutes to boot the machine, whereas before it might take a minute.

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Guest [Entry]

"The official limit for USB devices is 127 per controller... In theory, you should be able to plug hubs into hubs into hubs (they will each need their own power source) until you have 127 devices total.

This is the printed technical limitation from back when I was in college, but I've never seen anyone actually using more than 12 ports simultaneously.

As for startup times, yes... Having too many devices plugged in can cause a slow start-up. The PC will need to run its usual startup process, then mount each drive, etc...

If you aren't using all the drives constantly, I would leave them all unplugged and connect them as you need them. USB is hot-pluggable, so make sure the power switch is in the off position, plug it in to the wall and USB port, then turn the power on. This will keep your computer fast, save electricity, and extend the life of your drives.

For more info on the USB tech standard, you can check Wikipedia"