Re: single bit errors on files stored on USB-HDDs via USB2/usb_storage

[Matthias Schniedermeyer <ms@citd.de>]

DervishD wrote:
>     Hi Matthias :)
> 
>  * Matthias Schniedermeyer <ms@citd.de> dixit:
> 
>>My averate file size is about 1GB with files from about 400MB to
>>5000MB I estimate the average error-rate at about one damaged file in
>>about 10GB of data.
>>
>>I'm not sure and haven't checked if the files are wrongly written or
>>"only" wrongly read back as i delete the defective files and copy them
>>again.
>>
>>Today i copied a few files back and checked them against the stored MD5
>>sums and 5 files of 86 (each about 700 MB) had errors. So i copied the 5
>>files again. 4 of the files were OK after that and coping the last file
>>the third time also resulted in the correct MD5.
> 
> 
>     I had more or less the same issue a week or two ago. I performed
> lots of tests and only by replacing the USB2.0 PCI card, the USB cable
> and the power supply of the usb-hdd adapter got the problem solved.
> 
>     I'm not sure if the problem is really gone, but the system works now
> reliably. I don't know if sooner or later I'll get the issue again,
> because I didn't really identify a culprit: looks like the
> card+adapter+cable combination was just "ugly", and errors from the
> adapter were not reported correctly.

The 38 HDDs are in 38 enclosures, so each has it's own power supply. I
have used different cables and i replaced the USB-Controller once.

So it can't be a single faulty component. Except when the computer
itself would be the culprit.

>>NEVER did i see any messages in syslog regarding erros or an aborting
>>program due to errors passed down from the kernel or something like
>>that.
>
>     The same here! Looks like USB-HDD adapters don't report any errors
> to the kernel :?????
> 
>     The best advice I can give you, from my limited experience with the
> problem, is: replace the cable. This minimizes the chance of corrupted
> data getting into the adapter. If that doesn't solve the problem, try
> removing any unconnected cable that is plugged into the USB card.
> Believe it or not, a long but unconnected cable (put there just to be
> able to plug my USB card-reader without having to look for the cable in
> a drawer) was causing errors *even in a Kingston USB key that worked
> flawlessly otherwise*!!!

Hmmm. That's the only thing that i currently may be doing wrong.
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).

>     If you have any other question, feel free to drop me a note. I'm
> sorry I cannot give a much more technical or scientific answer, but
> unfortunately I have none :((

Thank you anyway.





Bis denn

-- 
Real Programmers consider "what you see is what you get" to be just as
bad a concept in Text Editors as it is in women. No, the Real Programmer
wants a "you asked for it, you got it" text editor -- complicated,
cryptic, powerful, unforgiving, dangerous.

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