Maximum number of external HDD's?

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blue-eye-boy

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Hey everyone, about a month ago I purchased 3 x 3tb WD external harddrives. I plugged in every one via usb. But the computer only "see" 2 of the drives. I mainly use it for cctv recording. When I unplug the one drive, and plug in the one which wasn't been seen, then that one is "seen", installed and working properly. But not all 3 together.

There is a total of 3 external drives working, then there's the 4th one I have this problem with, so in total 4 drives. Then there is also 2 internal hdd's.

I'm using windows 7 professional.

What can the problem be?

Thanks
 
My old work laptop mobo had too many devices powered by usb and shut down all the devices including its keyboard when I filled up the ports.
 
Roger Moore said:
My old work laptop mobo had too many devices powered by usb and shut down all the devices including its keyboard when I filled up the ports.
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Okay but can a desktop pc have too many usb devices? Currently it is the following using usb:
- Screen
- 3 External hdd's
- Mouse
- Keyboard
- Printer
 
Try using a self powered USB hub(one you plug into a wall socket for power)
 
Usb controllers can handle large number of devices per port providing they are self powered of course. So it's either power management side or the controllers.
 
supersunbird said:
Are you sure the two drives are not sharing the same drive letter?
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When I remove the one drive, and plug the "ghost" one in, it gets the same drive letter. But when I plug in all of them, that drive doesn't change to 6 gig, instead of 3 gig.

Aren't drive letters assigned automatically when a hdd is detected?

The, the hdd's are all self powered, so why would the usb power be an problem? Or are there still power drwan from usb, even if it is self powered?
 
Right click Computer - Management - Disk Management

Assign a different drive letter to the one HDD (3 gig) then add the 6 gig again.

My first thought was drive letters.

Can you see all the drives in Disk Management? Or Device Manager?
 
If they're all self powered then it's not a power issue it's something else.
 
Okay I did see it in the disk management list. It says the disk is offline, because it has a signature collusion with another disk that is online.

How can I resolve that?

Thanks so far
 
I changed the drive names, and it seems like it helped. Al 3 new ones, and the older external is online now.

Thanks a mil for the help!
 
jacqvt said:
I changed the drive names, and it seems like it helped. Al 3 new ones, and the older external is online now.

Thanks a mil for the help!
Click to expand...

:D

Normally the issue at a previous workplace was that someone who set the network/domain up had assigned a network drive the drive letter F. So if a PC had a C and D partition and a CD/DVD device was E then the F network drive and any USB stick would clash with that, that's how I know what the most likely problem was...
 
They should assign network drives from Z upwards and leave from A downwards for the drives.
 
It could also be that you're exceeding your USB bandwidth limit if each of the drives try to reserve bandwidth.

To check the bandwidth usage, go to Device Manager, browse to the Universal Serial Bus controllers and then open up the Universal Host Controller items and go to their Advanced tab.

I've also seen this kind of issue with internal drives where the PSU was on its way out, where it wouldn't pick up 2 of the 4 drives, unless you unplugged one of them.
 
Pada said:
It could also be that you're exceeding your USB bandwidth limit if each of the drives try to reserve bandwidth.

To check the bandwidth usage, go to Device Manager, browse to the Universal Serial Bus controllers and then open up the Universal Host Controller items and go to their Advanced tab.

I've also seen this kind of issue with internal drives where the PSU was on its way out, where it wouldn't pick up 2 of the 4 drives, unless you unplugged one of them.
Click to expand...
I checked that, it states 20 % system reserved, and 1% usb device. Dont think thats a problem? Anyway it's all working now.
 
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