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Glossary
EX800M
8.0 G
LOSSARY
Active LED Status — The WD drive supports external LED requirements. It provides an activity LED output
which is ON during command execution and OFF otherwise.
Annualized Failure Rate (AFR) — A method of measuring failure rates or trends for a group of units at a site.
The rates are based on the monthly total number of returned field failure units divided by the total cumulative
installed base and multiplied by 12 (to annualize the failure rate).
Automatic Defect Retirement — If defective sectors are found during a read or write, they are automatically
mapped out and relocated.
Block — A group of bytes handled, stored, and accessed as a logical data unit, such as an individual file record.
Buffer — A temporary data storage area that compensates for a difference in data transfer rates and/or data
processing rates between sender and receiver.
Data Lifeguard™ — Representing WD's ongoing commitment to data protection, Data Lifeguard data
protection utilities include thermal management, an environmental protection system, and embedded error
detection and repair features that automatically detect, isolate, and repair problem areas that may develop over
the extended use of the hard drive.
Data Transfer Rate — The rate that digital data is transferred from one point to another, expressed in bits per
second or bytes per second. Data Transfer Rate to Disk: The internal disk transfer rate in Mbits per second. Data
Transfer Rate from the Buffer to the Host: Based on the transfer of buffered data in MB per second.
Defect Management — A general methodology of eliminating data errors on a recording surface by mapping
out known bad areas of the media.
Data Path Protection (DPP) — A feature that prevents possible electronic failures by preventing corruption of
data on the hard drive.
Dual Stage Actuator (DSA) — DSA is an improvement to the overall capability of the Servo system and
provides a mechanical benefit to improve the response time (higher Bandwidth capability) of moving and
maintaining the head position over the data tracks.
ECC On-the-Fly — WD utilizes an LDPC hardware correction technique that corrects errors prior to host
transfer without any performance penalties. These error corrections are invisible to the host system because they
do not require assistance from the drive's firmware.
Error Correction Code (ECC) — A mathematical algorithm utilizing LDPC technology that can detect and
correct errors in a data field by adding check bits to the original data.
F.I.T. (Functional Integrity Testing) — A suite of tests WD performs on all its drive products to ensure
compatibility with different hosts, operating systems, application programs, and peripherals. This testing must
be performed before the product can be released to manufacturing.
Fluid Dynamic Bearings (FDB) — Bearing design that incorporates a layer of high-viscosity lubricant instead
of ball bearings in the hard drive spindle motor. FDB designs provide increased non-operational shock
resistance, speed control, and improved acoustics.
Formatted Capacity — The actual capacity available to store data in a mass storage device. The formatted
capacity is the gross capacity minus the capacity taken up by the overhead data required for formatting the
media.
Hot Plugging — The ability to swap out a failed hard drive without having to power down the system or reboot.
IntelliSeek — WD technology that proactively calculates an optimum seek speed to eliminate hasty movement
of the actuator that produces noise and requires power.
Latency — The period of time that the read/write heads wait for the disk to rotate the data to an accessible
position. For a disk rotating at 10,000 RPM, the average latency is 3 milliseconds.
Logical Block Address — An alternative addressing methodology of identifying a given location on a SATA
drive that permits disk sizes greater than 528 MB.
48
RELEASED 8/13/13
2679-771339-A05
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