Device Configuration Overlay (DCO)

How does a Device Configuration Overlay work?

Manufacturers and system integrators use the Device Configuration Overlay to make drives of different sizes appear uniform or to disable certain functions. There are dedicated ATA commands to query, set, reset or lock the setting until the next restart. A DCO can exist in addition to a Host Protected Area (HPA) . In that case the DCO area lies behind the HPA area at the end of the drive.

In newer versions of the ATA command specification, the feature was replaced by a successor mechanism. Many drives in the installed base still support it, however. The DCO therefore remains a known topic for forensics and secure erasure.

Significance for data erasure

Erasure software that only overwrites the capacity reported by the operating system does not reach the DCO area. Data, recovery partitions or deliberately hidden content can reside there. Reliable erasure methods therefore check before overwriting whether HPA or DCO are set, remove them and erase the full physical capacity. The result belongs in the erasure report. Which methods are otherwise important for HDD and SSD is shown in the guide Securely erasing hard drives and SSDs.

Second IT erases with Blancco and also captures hidden areas such as HPA and DCO. A digitally signed erasure certificate is issued for every device.

Frequently asked questions about the Device Configuration Overlay

What is the difference between HPA and DCO?

Both hide storage at the end of a hard drive. An HPA is often intended for recovery data and is easier to change. A DCO changes the drive's reported configuration more fundamentally and lies behind a possible HPA.

Can I detect a DCO myself?

With special software, the reported capacity can be compared with the actual capacity. Professional erasure software checks this automatically.

Does DCO also affect SSDs?

The feature originates from the ATA standard and can also occur on SATA SSDs. NVMe SSDs use a different command set.

What is a Device Configuration Overlay used for?

Manufacturers and system integrators use it to make drives of different sizes appear uniform or to disable certain functions. The hidden area remains physically present. It is invisible to the operating system and normal software.

Why does data in the DCO area remain after a normal erasure?

Erasure software that only overwrites the capacity reported by the operating system does not reach the DCO area. Reliable methods therefore check beforehand whether DCO or HPA are set, remove them and erase the full physical capacity.