Mar 8 09:36:35 bukvar kernel: [ 4491.964077] usb 5-5: reset high speed USB device using ehci_hcd and address 2
Mar 8 09:37:16 bukvar kernel: [ 4532.380243] usb 5-5: reset high speed USB device using ehci_hcd and address 2
Mar 8 09:37:50 bukvar kernel: [ 4566.228079] usb 5-5: reset high speed USB device using ehci_hcd and address 2
Mar 8 09:38:23 bukvar kernel: [ 4599.692070] usb 5-5: reset high speed USB device using ehci_hcd and address 2
Mar 8 09:38:56 bukvar kernel: [ 4632.432072] usb 5-5: reset high speed USB device using ehci_hcd and address 2
Mar 8 09:39:29 bukvar kernel: [ 4665.484084] usb 5-5: reset high speed USB device using ehci_hcd and address 2
Mar 8 09:40:01 bukvar kernel: [ 4697.384074] usb 5-5: reset high speed USB device using ehci_hcd and address 2
Mar 8 09:40:37 bukvar kernel: [ 4733.144073] usb 5-5: reset high speed USB device using ehci_hcd and address 2
Mar 8 09:42:27 bukvar kernel: [ 4843.796246] usb 5-5: reset high speed USB device using ehci_hcd and address 2
на второй минуте dd начал сыпать вот такими словами, при этом скорос упала с начальных 2,7 Mb/s до 600 Кбайт/с примерно.
и прерывалась эта ДД еще минуты 3 после SIGKILL
UPD: в /dev/null считалась без ошибок