Messages in this thread | | | Date | Sat, 09 Dec 2006 21:16:11 +1100 | From | Ben Nizette <> | Subject | Re: single bit errors on files stored on USB-HDDs via USB2/usb_storage |
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Oliver Neukum wrote: > Am Samstag, 9. Dezember 2006 07:11 schrieb Ben Nizette: >>>>> 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. :-| >>> You may have a bit pattern that stresses the controllers and suddenly >>> a marginal cable may matter. >> The errors occur in strings of 0xFFs. From the USB standard: >> >> a “1” is represented by no change in level and a “0” is represented by a >> change in level > > Yes, plus added stuffing bits. > >> so this error-infested bytes are effectively long, quiet times on the >> wire. I would have thought this would be the _least_ stressful time for >> the controllers but maybe they are also more susceptible to noise during >> this period. > > The longer you don't change the voltage the likelier are reciever and > transmitter to get out of sync.
Yes, hence the bit-stuffing, you're right :). And hence this period isn't really too stressful for the controller as the stuffed bits come relatively often.
We're hoping that any wire-errors get picked up by the CRC anyway so a marginal cable under any circumstances shouldn't silently corrupt data. I love that word 'shouldn't' ;)
Regards, Ben. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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