Western Digital Purple PR1334M, Technical Reference Manual

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Glossary WD Purple PR1334M
46 RELEASED 5/3/17 (WD CONFIDENTIAL) 2679-800084-A04
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).
Advanced Format (AF) — Technology adopted by WD and other drive manufacturers as one
of multiple ways to continue growing hard drive capacities. AF is a more efficient media for-
mat that enables increased areal densities.
AllFrame 4K — AllFrame 4K™ technology improves ATA streaming to help reduce frame loss,
improve overall video playback, and increase the number of hard drive bays supported within
a NVR.
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.
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 Life-
guard 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.
Defect Management — A general methodology of eliminating data errors on a recording sur-
face by mapping out known bad areas of the media.
Dual Stage Actuator Technology — A head positioning system with dual-stage actuators that
improves positioning accuracy over the data track(s). The primary stage provides course dis-
placement; the secondary stage uses piezo electric motion to fine tune the head positioning
to a higher degree of precision.
Dynamic Fly Height Control — This feature is designed to compensate for head/media sepa-
ration changes due to temperature and altitude. It adds margins across temperature and alti-
tude changes.
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.
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 manufac-
turing.
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.
Latency — The period of time that the read/write heads wait for the disk to rotate the data