Re: Installing Fedora 6 prerelease on a USB disk [SOLVED] -> now a GRUB problem !

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Andrea Mastellone wrote:
> However, I have solved the problem... in a strange fashion, but it
> works. External disk box was connected by means of a cable with two usb
> connectors to the computer (I guess that one connector is used only to
> supply electrical power). While both the cables were attached, the
> expert mode did not detect the disk. I then tried randomly to detach one
> connector.. and, magically, the disk has been dtected in the expert mode
> ! Evidently, the power requirement of the external disk is so low that
> only one cable is sufficient (infacts it is a 2.5" notebook drive).

It might be that this "cable" is presenting itself to the computer as an
unpowered hub, at least when both USB connectors are actually connected.
I suspect that it would need to talk USB to the computer somehow to
ensure that the computer continues to provide power to both sockets.

If that's the case, it's technically outside the USB specification to
have anything suitably high-powered attached to an unpowered hub. The
Linux kernel developers decided explicitly *not* to support this, in
case someone tries plugging a disk in and loses data because not enough
power is being supplied. (http://lwn.net/Articles/186331/).

You may want to follow the steps identified in that article to get
Fedora to actually power the hub from both USB ports -- as the article
says, you *don't* want power problems on a data storage device!

Hope this helps,

James.

-- 
E-mail:     james@ | Hooray. "I'm Sorry I Haven't A Clue" is back on, complete
aprilcottage.co.uk | with strip poker. Yes, this is on the radio.
                   | ("Erm..  five queens", "Barry, you're playing with
                   | postage stamps", "Oh.")                   -- Telsa Gwynne


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