linux-kernel - Re: single bit errors on files stored on USB-HDDs via USB2/usb

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Message-ID: <457940DC.90403@citd.de>
Date:	Fri, 08 Dec 2006 11:39:24 +0100
From:	Matthias Schniedermeyer <ms@...d.de>
To:	Stefan Richter <stefanr@...6.in-berlin.de>
Cc:	Robert Hancock <hancockr@...w.ca>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	DervishD <lkml@...vishd.net>
Subject: Re: single bit errors on files stored on USB-HDDs via USB2/usb_storage

Stefan Richter wrote:
> Matthias Schniedermeyer wrote:
> 
>>Robert Hancock wrote:
>>
>>>Matthias Schniedermeyer wrote:
>>>
>>>>I have a 1,5 Meter and a 4,5 Meter cable connected to the USB-Controller
>>>>and i only use of them depending on where the HDD is placed in my room,
>>>>the other one is dangling unconnected.
>>>>
>>>>Then i will unconnect the short cable and use the long cable exclusivly
>>>>and see if it gets better(tm).
> 
> BTW, I suspect front panel connectors could introduce noise too, via the
> jumper cables from motherboard to the panel.

It's a 5 port PCI-Addon-Card, no front panel connectors.
(The computers has only an OHCI/USB 1.1 controller onboard, which i use
for keyboard & mouse)

>>>That long cable could be part of the problem - I don't think the USB
>>>specification allows for cables that long (something like a 6 foot max
>>>as I recall).
>>
>>http://en.wikipedia.org/wiki/USB2
>>
>>Says that 5 meters are allowed.
> 
> 
> I don't know about USB 2.0, but in case of FireWire, ~4.5m long cables
> are theoretically in spec too. I've got a FireWire 400 and a FireWire
> 800 cable this long, and both don't work very unreliable. Depending on
> what's connected, they fail sooner or later. However due to how FireWire
> works, this is immediately noticed as data CRC errors or bus resets.
> I.e. it's nearly impossible for noisy hardware to _silently_ cause data
> corruption. I would suppose USB has similar CRC checks.
> 
> Also, you mentioned that the corruption occurs systematically on certain
> byte patterns. Therefore it's certainly not related to the cables.

It'd guess that too, but who can that say for sure. :-|





Bis denn

-- 
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