Maxtor ATLAS 10K III - Manual (Page 273)

Glossary
Maxtor Atlas 10K III 18/36/73 GB Ultra160 SCSI G-7
MICROPROCESSOR – The integrated
circuit chip that performs the bulk of data
processing and controls the operation of all of
the parts of the system. A disk drive also
contains a microprocessor to handle all of the
internal functions of the drive and to support
the embedded controller.
MICROSECOND (µs) – One millionth of a
second (.000001 sec.).
MILLISECOND (ms) – One thousandth of a
second (.001 sec.).
MTBF – Mean Time Between Failure.
Reliability rating indicating the failure rate
expected of a product expressed in power on
hours (POH). Since manufacturers differ in the
ways they determine the MTBF, comparisons
of products should always take into account the
MTBF calculation method.
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.
.NANOSECOND (ns) – One billionth of a
second (0.000 000 001 second or 10-9 second).
NEXUS – A relationship between two devices
that begins with the establishment of an initial
connection and ends with the completion of an
I/O process. A nexus relationship is further
defined by the letters I (initiator), T (target), L
(logical unit), R (target routine), x (either L or
R), Q (queue tag), and x_y (either an x or a Q)
OVERHEAD – Command overhead refers to the
processing time required by the controller, host
adapter, or drive prior to the execution of a
command. Lower command overhead yields
higher drive performance. Disk overhead refers
to the space required for non-data information
such as location and timing. Disk overhead
often accounts for about ten percent of drive
capacity. Lower disk overhead yields greater
disk capacity.
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.
PARITY – An error checking technique
wherein the sum of the bits in a data byte is used
to set or reset an extra parity bit, depending on
whether the sum is an odd or an even number.
A second parity check after the data is
transferred to a new location checks that the
new parity bit matches the transferred bit. Parity
checking can only detect an odd number of bit
errors (1,3,5, etc.). Parity is defined as odd or
even, depending on which condition (odd or
even) is used to set the parity bit.
PARKING ZONE – A position in a non-data
area on a disk platter reserved for resting the
heads when power is off. Using this area
prevents the heads from touching the surface in
data areas upon power down, adding to the data
integrity and reliability of the disk drive. The
parking zone is most often inside the disk's
inner-most cylinder.
PARTITION – A portion of a hard disk
dedicated to a particular operating system and
application and accessed as a single logical
volume.
PERFORMANCE – A measure of the speed
of the drive during normal operation. Factors
affecting performance are seek times, transfer
rate and command overhead.