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External Hardrive between 2 PCs
- Thread starter Urukarch
- Start date
Lord Evermore
Diamond Member
You can't use them both at the same time. USB is a master/slave setup.
Firewire can be used to give access to both, if you've got two ports on the drive, because every Firewire device is a master.
There are USB switches so you can go back and forth, but only one can use it at a time.
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Firewire can be used to give access to both, if you've got two ports on the drive, because every Firewire device is a master.
There are USB switches so you can go back and forth, but only one can use it at a time.
Cheapest on Newegg.com: http://www.newegg.com/Product/Product.asp?Item=N82E16817107510
AMCRambler
Diamond Member
In order to connect one USB drive to two computers you'd need to have a usb hub there. And I have no idea what would happen, but since the USB bus also supplies power, I can't imagine it would be very good. You'd probably fry both usb controllers on the computers.
And yes the usb switch would just be a simple AB switch with a selector button
Lord Evermore
Diamond Member
A USB hub can't be used for this purpose. A hub only has one uplink port to one PC. There's no way to connect to two PCs. Even if you made a splitter for the uplink, I don't think it would cause any damage to anything (it would just be a parallel circuit), but it most likely would not work, since the USB device only can function with a single master controller, and would be getting conflicting signals from the two PCs. It would probably work if only one was turned on at the same time, but still could cause problems since when you turn an ATX system "off", it's still got power to the mainboard, and may be set to sense USB activity.
Any USB switch would have to be OS independent. The linked switch is manual by pressing a button (which means it's just an electrical switch, rather than a physical switch, which is good). Others are controlled with a key combination on the keyboard (like hitting scroll-lock twice within 2 seconds). All 3 are also methods that regular KVM units are controlled.
That switch also looks like it may have a big brother model, which would allow 4 PCs to be connected. Looks like they just used the same outer shell, unless those two outside lights are activity lights, which would be pointless.
Bob Anderson
Member
I used an Acomdata USB external drive with two computers for over a year until I finally got tired of switching the USB cable from one computer USB port to the other computer's USB port.
Naturally, you must 'safely remove hardware' and shut the external down before switching the USB cable from one computer to the other one.
However, I got tired of doing this and one day I nearly tipped the Acomdata over, so I bought a second external USB drive.
-Bob
Lord Evermore
Diamond Member
Windows (and probably other OSes) automatically configure removeable drives for "quick removal", meaning the OS does not cache data before sending it to the drive. You have to manually set it to use caching. The quick removal setting means you can just unplug the drive without having to use Safely Remove Hardware, and Windows won't bitch. As long as the drive hasn't been transferring any data for a few seconds, there should be no issue with the cache on the drive itself not having been written to disk.
What if an external hard drive has both firewire and usb (or even two usb) ports and you connect it to two separate computers, then accidently have both running at the same time.
No risk of physical damge, just probably some error message from the second recognized computer?
No risk of physical damge, just probably some error message from the second recognized computer?
Lord Evermore
Diamond Member
No device has more than one upstream connector, except a switch. The upstream is the connector that's sort of square with two corners rounded. You CANNOT connect a device to two different computers with USB. If you have multiple USB connectors, it's just because that device can act as a hub for other devices to plug into, as USB can be daisy-chained.
I'm not sure what would happen if you connected it by Firewire and USB at the same time. Most likely an error of some sort, but no damage. It might depend on whether there's a single bridge chip inside, or one for the USB and one for Firewire. I doubt it would work, since the drive would be receiving conflicting commands from the two PCs, even though they might be able to communicate with the control board at the same time.
I'm not sure what would happen if you connected it by Firewire and USB at the same time. Most likely an error of some sort, but no damage. It might depend on whether there's a single bridge chip inside, or one for the USB and one for Firewire. I doubt it would work, since the drive would be receiving conflicting commands from the two PCs, even though they might be able to communicate with the control board at the same time.
Bob Anderson
Member
You are right. I got into the habit of SRH and shuting the External off before switching, but as you point out that isn't necessary if the external is configured for quick removal.
I just wanted to be on the safe side but I was overdoing it, I realize now.
-Bob
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