HDD (Festplatte)

It works in old PCs, in servers, in network storage and in many multifunction printers: the classic hard drive. Even though SSDs have long been standard in notebooks, many HDDs still run in companies. When decommissioning, they behave differently from flash storage.

Structure and how it works

In a hermetically sealed or helium-filled housing, one or more coated discs, the platters, rotate. Typical speeds are 5,400 or 7,200 revolutions per minute, and 10,000 or 15,000 for server drives. A read/write head floats close above each disc surface and magnetizes tiny areas. A controller translates the computer's commands and manages the sectors. IBM introduced the first commercial hard drive in 1956.

Common form factors are 3.5 inches for desktop PCs and servers and 2.5 inches for notebooks. HDDs are usually connected via SATA or, in servers, via SAS.

HDD and SSD compared

Feature	HDD	SSD
Storage principle	Magnetic, rotating discs	Electronic, flash memory cells
Moving parts	Yes	No
Speed	Lower, especially for access times	Significantly higher
Cost per terabyte	Lower	Higher
Secure erasure	Overwriting all sectors is effective, including hidden areas	Firmware commands or Crypto Erase required
Degaussing	Possible, drive unusable afterwards	Ineffective

There are also hybrid drives (SSHD) that combine an HDD with a small flash cache.

What to note when retiring devices

• Erasing: A complete Overwriting with subsequent verification renders data on functioning HDDs unreadable.
• Hidden areas: the Host Protected Area (HPA) and the Device Configuration Overlay can hide storage from the operating system.
• Defective sectors: Reallocated sectors may contain old data. Good erasure software detects them.
• Defective drives: If an HDD cannot be fully addressed, only destruction remains, for example under DIN 66399 in material class H.
• Forgotten devices: Printers, copiers, video recorders and NAS systems often contain hard drives too.

Which methods suit which drives is described in the guide Securely erasing hard drives and SSDs. For the destruction levels see DIN 66399.

HDDs at Second IT

Second IT erases HDDs with Blancco. Hidden areas such as HPA and DCO as well as reallocated sectors are also detected and erased. Each device receives a digitally signed erasure certificate. Defective hard drives are destroyed in-house in accordance with DIN 66399 (up to security level H-5 and E-5). More on certified data deletion.

Frequently asked questions about the HDD

What is the difference between an HDD and a hard drive?

None. HDD stands for hard disk drive, the technical term for the classic hard drive. Colloquially, "hard drive" is sometimes also used for SSDs, but technically these are different types of storage.

How long does an HDD last?

That depends on usage, temperature and design. Manufacturers state an expected lifespan or failure rate. S.M.A.R.T. values, such as the number of reallocated sectors, give indications of the condition.

Is it enough to format an HDD?

No. When formatting, the data usually remains completely intact. What is needed is overwriting all sectors with verification or physical destruction.

How do HDDs and SSDs differ when erasing?

For an HDD, overwriting all sectors is effective, including hidden areas. For SSDs, firmware commands or Crypto Erase are required. Degaussing only works on HDDs and renders them unusable.

Do printers and copiers also have an HDD?

Often yes. Multifunction printers, copiers, video recorders and NAS systems also frequently contain hard drives. They are easily forgotten during decommissioning even though data may be stored on them.