Zero-sized devices

Every once in a while, I get a support request involving a zero-sized device. That means the device is displayed in a device list of ZAR or one of Klennet tools, its indicated size is 0 (zero). Most often, that would be some USB device, a USB stick, or a memory card (even with a card reader built into the laptop, memory cards are almost always routed via USB). On rare occasions, a SATA device may behave the same.

When you try to recover data, it looks like the device is there, but

  • ZAR and Klennet tools list it with a 0 (zero) size but with a seemingly valid name1.
  • Disk Management lists a physical drive with a capacity of 0.
  • Other data recovery tools may or may not list the device at all.
  • No data recovery tool can scan the device. There may be an explicit error message, or the scan may complete instantly with no files found, depending on the specific software.

If you see this behavior, the device cannot be recovered with software.

There are different possible reasons,

  • In an external SATA-to-USB box, the converter, converter-to-drive connection, or the drive itself had failed.
  • In a USB flash drive, the memory controller may have failed, or the NAND chips, or the connection between these.
  • A monolithic SD card is, in principle, similar to a flash drive but if it fails, you are worse off than with a PCB-based flash drive.

There is only one thing you can try with a zero-sized device. If it is a USB external enclosure with a SATA hard drive inside, you can disassemble the enclosure (NOT the hard drive itself) and connect the drive directly to a SATA port of a desktop PC. If that does not help, or if the drive is not a SATA-compatible external, the recovery must be performed by a lab with proper hardware tools.

1The device name as displayed may be correct. It may also display a device family name or something generic like USB Mass Storage Device. The family name may be difficult to distinguish from the correct device name. The exact behavior depends on the device and the damage.

Filed under: USB.

Created Friday, October 6, 2017

Updated 20 May 2018