A service area is a logical area on the hard-drive (residing on the platters)
set aside by hard-drive vendors for internally managing the drive.
These areas are outside the hard-drive’s Logical Block Address (LBA) space and as
such are non-addressable and inaccessible via the standard ATA commands.
The service area contains both code and data modules, such as defect management
modules, SMART data modules, self-test modules and much more.
A common overview of the disk areas is as follows:
In order to access the service area, Programmable IO must be used to
send commands directly to the hard-drive’s IO port. These commands are unique
to the hard-drive vendor and are not publicly disclosed, used rather by
released vendor tools (and by some sophisticated viruses such as
Disk Firmware Area (DPA)
In most cases this area is the one that is called service area.
The firmware is composed of a series of modules. Examples are:
SECU (Security System Module), P-List, G-List, T-List, SMART Attributes,
and U-List (Firmware Zone Translator).
See also Bad sector remapping.
A portion of the disk firmware is usually resident on the drive, loaded on power up
by code located on the controller board of the hard-drive and managing the disk until
the disk is shutdown,
or sometimes residing in flash memory located on the disk controller chip.
Host Protected Area
The Host Protected Area (HPA) is used for holding diagnostics and other
utilities required by the manufacturer such as the boot sector,
the exact content depending upon the manufacture.
It may contain information about the user addressable sectors, start of the
reserved area, and the code for the boot.
Device Configuration Overlay
A Device Configuration Overlay (DCO) is similar to the HPA, but is used by
manufacturers to configure drive sizes and may exist at the same time.
Its purpose is to allow the PC manufacturers to purchase
one disk and market it as different models of different sizes.
It can also be used to enable and disable features on the disk.