Device Configuration Overlay

Device Configuration Overlay (DCO).

• added in ATA-6.

• with DCO, both BIOS and OS see the same size.

• DCO removable is permanent (HPA remotion can be temporary).

• allows to hide the disk's real capacity.

  • PC makers can buy different brands of discs with different sizes and set them to be the same size.

• HPA and DCO can coexist on the same disk.

Identify DCO

• on the Linux command line: hdparm --dco-identify /dev/sdX

• compare values with: hdparm -Iv /dev/sdX

Remove a DCO area

Linux command line:

• with hdparm tool.

• it is possible to remove, but not to create a new one.

• WARNING – it can destroy data permanently.

• to remove DCO and set the disk with the real size.

  • hdparm --yes-i-know-what-i-am-doing --dco-restore /dev/sdX