[mdlug] USB Flash Drive Recommendations for Linux?

[Aaron Kulkis]

Robert Citek wrote:
> On Wed, Feb 18, 2009 at 12:15 AM, Raymond McLaughlin
> <driveray at ameritech.net> wrote:
>> To avoid this hazard I make it a practice to connect the USB last, and
>> disconnect it first, while supplying power to the drive with a dedicated
>> supply.
> 
> A few questions:
> 
> 1) are you saying I can power a laptop SATA drive over USB?  If so, how?

Yes.  The power comes off of the USB plug

> 2) how do I connect an external power source to a laptop IDE drive?
> 3) how can I tell if my IDE drive is putting undue power strain on the
> USB circuit?
> 
> I've been using the IDE laptop drive with the IDE/USB adapter for well
> over a year and it's been working flawlessly.

And that's a great solution for an external drive which is only
detached occasionally -- such as the situation we had in Baghdad,
where the primary computer for the Operations office was a laptop
with a 40 GB internal disk, and significantly more storage space
was needed.  For reasons of practicality and DOD regulations, we
couldn't replace that drive with any of the larger (60, 80, 100,
120 GB) laptop drives available from a vendor on base, but we
COULD attach additional storage in the form of an external disk.

>                                              The drive is never hot,
> nor is the cable nor the connectors.

Ray was talking about the USB hub chip which is internal to
the computer when a device with high drain off of the USB power
connectors is hooked up to a USB port.

>                                        However, I would like to upgrade
> it to one of the larger SATA varieties but haven't figured out how (or
> even if) to power it over USB.  I'm guessing the USB lapotop enclosure
> variety has split the USB bus into SATA data and SATA power.

USB has 5 electrical connections: a surrounding Ground connection
and 4 internal connectors:
	1.  Power (+)
	2.  Data-
	3.  Data+
	4.  Power (-)

Pins 1 and 4 are specifically for the purpose of powering
external devices.  Due to USB device loads, SOME external hubs
have an external power supply to reduce the power load on
the internal hub.
http://en.wikipedia.org/wiki/USB#Types_of_USB_connector


SATA has 7 electrical connections on the data connector,
and 15 pins on the power cable.  I have one laptop SATA
disk in a USB carrier, and the internal circuitry does
what is necessary to produce the proper power pin voltages
and to convert the data signals.

Data:
Pin # 	Function
1 	Ground
2 	A+ (Transmit)
3 	A- (Transmit)
4 	Ground
5 	B- (Receive)
6 	B+ (Receive)
7 	Ground
- 	coding notch