XL500S
Glossary
2679-701211-A06
RELEASED 10/21/10 (WD CONFIDENTIAL)
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8.0
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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.
Command Queuing
— See
Native Command Queuing (NCQ)
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.
ECC On-the-Fly
— A hardware correction technique that corrects errors in the read buffer 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 that can detect and correct errors in a
data field by adding check bits to the original data.
Femto Slider
— These drives incorporate the femto slider form factor in which the read/write head is
mounted on the small, lightweight femto slider which allows the head to move more quickly from track
to track on the disk.
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.
