Western Digital Purple PR1200M Technical Reference Manual page 56

Glossary
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
to an accessible position. For a disk rotating at 10,000 RPM, the average latency is 3
milliseconds.
IntelliSeek — WD technology that proactively calculates an optimum seek speed to eliminate
hasty movement of the actuator that produces noise and requires power.
Logical Block Address — An alternative addressing methodology of identifying a given
location on a SATA drive that permits disk sizes greater than 528 MB.
Native Command Queuing (NCQ ) — NCQ allows the drive to re-order read commands,
thereby increasing random read IOPs. NCQ is a true Enterprise feature for environments such
as database, Web servers, and e-mail servers.
NoTouch™ Ramp Load Technology
ensuring significantly less wear to the recording head and media as well as better drive
protection in transit.
Preemptive Wear Leveling (PWL) — WD feature that provides a solution for protecting the
recording media against mechanical wear.
PRML (Partial Response Maximum Likelihood) — A read channel using sampled data, active
equalization and Veterbi detection to accurately retrieve the user data off the disk.
RoHS (Restriction of Hazardous Substances) — WD hard drive products manufactured and
sold worldwide after June 8, 2011, meet or exceed Restriction of Hazardous Substances
(RoHS) compliance requirements as mandated by the RoHS Directive 2011/65/EU.
Rotational Latency — The amount of delay in obtaining information from a disk drive that can
be attributed to the rotation of the disk. For a disk rotating at 10,000 RPM, the average
latency is 3 milliseconds.
RPM (Revolutions per Minute) — Rotational speed of the media (disk), also known as the
spindle speed. Hard drives spin at one constant speed. The slower the RPM, the higher the
mechanical latencies. Disk RPM is a critical component of hard drive performance because it
directly impacts the rotational latency of the disk transfer rate.
Seek Time — The time it takes for the read/write head to move to a specific block of data on
the hard drive. The average seek time is computed by dividing the time it takes to complete
a large number of random seeks by the number of seeks performed.
Sector — A 512-byte packet of data.
Self-Monitoring, Analysis, and Reporting Technology (S.M.A.R.T.) — A technology to assist
the user in preventing possible system down time due to hard drive failure.
Serial ATA (SATA) — SATA is the industry standard bus interface for hard drives. It is designed
to replace Parallel ATA, and has many advantages including increased transfer rate, improved
signal integrity, enhanced data protection, and hot plugging.
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.
Staggered Spinup — SATA feature that allows the system to control whether the drive will
spin up immediately or wait until the interface is fully ready.
Unrecoverable Error — A read error that cannot be overcome by an ECC scheme or by
rereading the data when host retries are enabled.
World Wide Name (WWN) — 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
46
— The recording head never touches the disk media
RELEASED 5/4/17 (WD CONFIDENTIAL)
WD Purple™ PR1200M
2679-800065-A03