Maxtor Computer Drive - Manual (Page 64)

GLOSSARY
Maxtor DiamondMax 8S 40GB SATA G-6
PLATED MEDIA – Disks that are covered
with a hard metal alloy instead of an
iron-oxide compound. Plated disks can store
greater amounts of data in the same area as a
coated disk.
PLATTER – An disk made of metal (or
other rigid material) that is mounted inside a
fixed disk drive. Most drives use more than
one platter mounted on a single spindle (shaft)
to provide more data storage surfaces in a
small package. The platter is coated with a
magnetic material that is used to store data as
transitions of magnetic polarity.
POH – Acronym for power on hours. The unit
of measurement for Mean Time Between
Failure as expressed in the number of hours
that power is applied to the device regardless
of the amount of actual data transfer usage.
See MTBF.
POSITIONER – See actuator.
R
RAM – Acronym for random access memory.
An integrated circuit memory chip which
allows information to be stored and retrieved
by a microprocessor or controller. The
information may be stored and retrieved in
any order desired, and the address of one
storage location is as readily accessible as any
other.
RAM DISK – A “phantom disk drive” for
which a section of system memory (RAM) is
set aside to hold data, just as if it were a
number of disk sectors. The access to this data
is extremely fast but is lost when the system is
reset or turned off.
READ AFTER WRITE – A mode of
operation that has the computer read back
each sector on the disk, checking that the data
read back is the same as recorded. This slows
disk operations, but raises reliability.
READ VERIFY – A disk mode where the
disk reads in data to the controller, but the
controller only checks for errors and does not
pass the data on to the system.
READ/WRITE HEAD – The tiny
electromagnetic coil and metal pole piece
used to create and read back the magnetic
patterns (write or read information) on the
disk. Each side of each platter has its own
read/write head.
REMOVABLE DISK – Generally said of
disk drives where the disk itself is meant to be
removed, and in particular of hard disks using
disks mounted in cartridges. Their advantage
is that multiple disks can be used to increase
the amount of stored material, and that once
removed, the disk can be stored away to
prevent unauthorized use.
RLL – Run Length Limited. A method used
on some hard disks to encode data into
magnetic pulses. RLL requires more
processing, but stores almost 50% more data
per disk than the MFM method.
ROM – Acronym for read only memory.
Usually in the form of an ROM in the
controller that contains programs that can be
accessed and read but not modified by the
system.
ROTARY ACTUATOR – The rotary
actuator replaces the stepper motor used in the
past by many hard disk manufacturers. The
rotary actuator is perfectly balanced and
rotates around a single pivot point. It allows
closed-loop feedback positioning of the heads,
which is more accurate than stepper motors.
ROTATIONAL LATENCY – The delay
between when the controller starts looking
for a specific block of data on a track and
when that block rotates around to where it
can be read by the read/write head. On the
average, it is half of the time needed for a full
rotation (about 8 ms.).
S
Serial ATA (SATA) - Serial ATA (Serial
Advanced Technology Attachment or SATA)
is a standard for connecting hard drives to
computers. The Serial ATA standard defines a
physical interface that uses serial signaling
technology unlike the ATA standard
(sometimes referred to as Parallel ATA that
uses parallel technology.