USB vs. direct attachment

If you need to recover data from the standard hard drive in the USB enclosure, it is useful to get the drive out of the enclosure and connect it directly to the appropriate port on the PC motherboard.

USB enclosure includes an USB-to-IDE converter - a special controller which translates commands coming via USB bus to the appropriate IDE commands and sends them to the drive. As the drive responds to commands, the controller translates the responses back to what the USB bus understands.

This adds additional layer of complexity to the system. As long as the system works normally, this is just fine. However, if a problem develops, we obviously want to get rid of this extra complexity.

  • The enclosure itself may fail. In this case, connecting a drive directly to the motherboard port gives you data back immediately.
  • If there is a separate power supply to the enclosure (it is usually the case with 3.5 inch boxes), the power supply may degrade to the point it does not provide sufficient power for a drive to work properly.
  • The converter chip in the enclosure may go bad, and stop doing the translation properly.
  • Certain chips are not very good in translating error responses from the drive. So the enclosure works fine as long as the drive is fine. When there is a bad block on the drive, the converter chip fails to report this correctly back to the host machine. This causes an enclosure to disconnect completely, and you may need to replug an enclosure or even reboot to read some more data from the drive. On the other hand, an integrated motherboard disk controller would just process the drive error report and continue normally.

Considering all the above, it is recommended that you avoid using USB enclosures for data recovery if practical.

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