Maxtor Atlas SCSI Drive 15K II, Руководство по эксплуатации продукта

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Glossary
Maxtor Atlas 15K G-9
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.
RECONNECT – The act of reviving a nexus to
continue an I/O process. An initiator
reconnects to a target using the SELECTION
and MESSAGE OUT phases after winning
arbitration. The target reconnects to the
initiator using RESELECTION and
MESSAGE IN phases after winning
arbitration.
RECONNECTION – The state which results
from a reconnect. It exists from the assertion of
BSY in the SELECTION or RESELECTION
phase and lasts until the next BUS FREE phase.
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 – Abbreviation for Run Length Limited.
An advanced method used to encode (or
compress) data for storage on a disk. RLL
encoding stores almost 50 percent more data
than MFM (Modified Frequency Modulation).
RLL code improves MFM code by encoding
data bits in groups rather than singly. Many
encoding schemes are possible. The best
achieve optimum values of code rates,
clocking, power spectrum, error propagation
and encoding complexity. A number pair (e.g.,
1,7) is usually stated with RLL references. It
refers to the minimum number of 0;s(1) and the
maximum number of 0's (7) that can separate
data 1's stored on the disk.
ROM – Read-Only Memory. Integrated circuit
memory chip containing programs that can be
accessed and read but can not be modified.
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 average, it is half of the
time needed for a full rotation (about 8 ms.).
S
SCA – Single Connector Attachment. A drive
connector that combines the signal and power
connectors into one. Typically, SCA-type
connectors are used in RAID (Redundant
Array of Inexpensive Devices) systems.
SCA-2 – An improved Single Connector
Attachment that incorporates two electrostatic
discharge (ESD) pins on either end of the
connector to improve safety when making a
connection.
SCAM-1 – SCSI Configured Automatically. A
plug-and-play method used in some drives.
SCSI – Small Computer System Interface. An
interface designed for Apple Macintosh
systems and UNIX workstations.
SCSI-1 – The first small computer system
interface standard.
SCSI-2 – An enhanced small computer system
interface as defined and published by ANSI in
standard X3.131-1994. One of the major
features of SCSI-2 is integrating the controller
into the peripheral device, making the device
independent of the initiator.
SCSI-3 – A new set of related ANSI standards
are currently under development by the X3T10
committee. The old SCSI-2 standard has been
divided into a new set of standards for SCSI-3.
Some of these [working draft] standards are:
SAM (SCSI Architecture Model) for the
architecture;
SBC (SCSI Block Commands) for the disk
drive specific command set.
SPC (SCSI Primary Commands) for the
primary command set; and