Maxtor D540X-4G - Manual (Page 52)

Glossary
G-6 Maxtor D540X-4G
MTTR – Mean Time To Repair. The
average time it takes to repair a drive that has
failed for some reason. This only takes into
consideration the changing of the major
sub-assemblies such as circuit board or sealed
housing. Component level repair is not
included in this number as this type of repair
is not performed in the field.
N
NANOSECOND (ns) – One billionth of a
second (0.000000001 second).
O
OVERHEAD – The processing time of a
command by the controller, host adapter or
drive prior to any actual disk accesses taking
place.
OVERWRITE – To write data on top of
existing data, erasing it.
OXIDE – A metal-oxygen compound. Most
magnetic coatings are combinations of iron or
other metal oxides, and the term has become
a general one for the magnetic coating on tape
or disk.
P
PARTITION – A portion of a hard disk
devoted to a particular operating system and
accessed as one logical volume by the system.
PERFORMANCE – A measure of the speed
of the drive during normal operation. Factors
affecting performance are seek times, transfer
rate and command overhead.
PERIPHERAL – A device added to a system
as an enhancement to the basic CPU, such as
a disk drive, tape drive or printer.
PHYSICAL FORMAT – The actual
physical layout of cylinders, tracks, and sectors
on a disk drive.
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
REDUNDANT ARRAY OF
INDEPENDENT DISKS (RAID)
- is a
way of storing the same data in different places
(thus, redundantly) on multiple hard disks. By
placing data on multiple disks, I/O operations
can overlap in a balanced way, improving
performance. Since multiple disks increases
the mean time between failure (MTBF),
storing data redundantly also increases
fault-tolerance.
A RAID appears to the operating system to be
a single logical hard disk. RAID employs the
technique of striping, which involves
partitioning each drive's storage space into
units ranging from a sector (512 bytes) up to
several megabytes. The stripes of all the disks
are interleaved and addressed in order.
RAID – See redundant array of independent
disks
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