Ultrastar 7K2
HGST Hard Disk Drive Technical Reference Manual
24
S.M.A.R.T. Command Transport (SCT)
The SCT Command Transport feature set provides a method for a host to send commands and data to a
device and for a device to send data and status to a host using log pages. Standard ATA commands may
be interspersed with SCT commands, but SCT commands cannot be nested. SCT commands that do not
require a subsequent data transfer operation are not interspersed with any ATA commands or each other.
The SCT Command Transport feature set provides a method for a host to send commands and data to a
device and for a device to send data and status to a host using log pages. This capability is used to pass
commands through a driver interface or a bridge where new or unknown commands may be filtered and
not passed to the drive. SCT is also used for issuing commands that require more than 8 parameter bytes.
ATA8-ACS provides detailed information on the usage and capabilities of SCT. The SCT feature set
includes the following commands:
Write Same
Temperature Reporting
Write Same
The Write Same command allows the host to erase the media, or write a pattern repeatedly across the
media, with a minimum of data transfer from the host. The host can clear the entire media to zeros or a
specific pattern by sending this command with the pattern as a parameter—no data transfer is necessary.
Write Same can write the entire media, or just a portion of the media. The host can monitor the progress of
the Write Same by issuing SCT Status requests. This frees the host system to do other tasks while the
media is being cleared.
Temperature Reporting
The SCT Temperature Reporting (SCT TR) feature allows a host system to access temperature
information in the drive. The S.M.A.R.T. temperature value is reported within ±3°C of the base casting
temperature. This information can been used to control fans or adjust the usage of various system
components to keep the drive within its normal operating temperature. Applications include Enterprise,
Laptop, Desktop and Consumer Electronics. SCT TR reports the maximum and minimum sustained
operating limits, warning level limits, and drive damage limits. In addition to reporting the limits, SCT TR
returns the current drive temperature (a temperature history which the host can use to predict heating or
cooling trends) and the maximum temperature achieved during the lifetime of the drive as well as the
highest temperature achieved since the power was applied to the drive. Detailed information on this
capability can be found in ATA8-ACS.
World Wide Name (WWN)
It has become a critical requirement that hard drives be uniquely identified by computer systems. This
allows a drive to maintain its identity as it is transported from system to system or placed on a network. IEEE
has defined a format for serial numbers that is widely recognized in the computing industry by adding
World Wide Name (WWN) to ATA/ATAPI-7 in 2002.
The World Wide Name (WWN) defined in ATA/ATAPI-7 is a modification of the IEEE Extended Unique
Identifier 64 bit standard (EUI-64) and is comprised of three major components: naming authority,
organizationally unique identifier (OUI) and serial number. This product’s OUI is 0014EEh.
Power Loss Data Protection
Upon power loss, the drive utilizes stored spindle energy to back up the HDD cache to on- board flash.
This allows deeper write queues which boosts performance, while minimizing data loss/ corruption such
as write splices that can occur during unexpected power losses.
