Clustering
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Compatible
FireWire
Hot
Swap Benefit
RAID
Overview
RAID
Comparison
Repeater
Benefits
SAN
Overview
Termination
Basics
Interface
& Connector
Reference
SCSI
Connectors
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Storage Dictionary
- packet
- A group
of bits, packaged together, for transmission purposes. Three
principal elements are included in the packet: (1) control
information-destination, origin, length of packet, etc.;
(2) the data can be transmitted; and (3) error detection
and correction bits. Sending data in packets rather than
continuous streams offers more efficient use of transmission
lines.
- parallel
interface
- The
transmission of bits over multiple wires at one time. Accomplished
by devoting a wire for each bit of a byte. Parallel data
transmission is very fast, but usually practical only for
short distances, typically under 500 feet, because of the
need for heavy cable. Most often used in computer-to-printer,
scanner-to-computer, and other host-to-peripheral applications.
- parallel
transmission
- The
simultaneous transmission of bits over multiple fibers.
Accomplished by devoting a fiber for each bit. Parallel
data transmission is very fast, but usually is practical
only for short distances (typically under 500 feet) because
of signal recovery and signal quality problems. Contrast
with serial transmission.
- parity
- An
extra bit, added to a number, used for checking the accuracy
of binary numbers. Odd parity means that the sum of all
1's in the number, including its corresponding parity bit,
is odd.
- payload
- That
portion of the data field in a frame left after removing
any optional headers.
- peripheral
device
- A device
that can be attached to a host computer, using a SCSI bus
for example. Typical SCSI peripherals are disk drives, tape
drives, printers, and communication devices.
- plotter
- An
output device for drawing maps or engineering drawings.
- point-to-point
- A topology
where exactly two ports communicate.
- port
- A connection
to a bus. An access point for data entry or exit. A connector
on a device to which other cable devices are attached. Also
referred to as an adapter. The single-byte SCSI bus (SCSI-1)
allows eight ports; the 16-bit SCSI-2 WIDE bus allows sixteen
ports. For Fibre see N_Port, NL_Port, F_Port, and FL_Port.
- primitive
sequence
- A transmission
word defined by Fibre Channel that conveys special control
information between ports on a link. A primitive sequence
is recognized when three adjacent transmission words of
the same value are received.
- primitive
signal
- A transmission
word defined by Fibre Channel that conveys control information
between ports on a link. A primitive signal is recognized
when only one transmission word is received.
- priority
- The
ranking of the devices on the SCSI bus during arbitration.
The higher numbered IDs have higher priority.
- PROM
- Programmable
Read Only Memory.
- protocol
- A convention
for data transmission that defines timing, control, formatting
and data representation.
- RAID
- Redundant
Array of Inexpensive, or Independent Discs. A storage device
that uses several magnetic or optical discs in tandem to
increase bandwidth output and to provide redundant backup.
For more information Browse to RAID
Overview
- reassembly
- A process
of reordering and extracting the payload fields from frames
in a sequence to reconstruct a copy of a source buffer in
a destination buffer.
- receiver
- The
circuitry that receives electrical signals on a line. Also,
the ultimate destination of data transmission.
- reconnect
- The
function that occurs when a SCSI Target reselects a SCSI
Initiator to continue an operation. A reconnect operation
would typically be preceded by a disconnect. See also "reselect".
- record
- A record
is a group of related items treated as one unit of information.
For example, policyholder's name, address, social security
number, etc. Each item in the record is a field.
- repeater
- A device
that amplifies or regenerates the data signal in order to
extend the transmission distance.
- reselect
- Action
by a target or an initiator to reestablish a connection,
after a disconnect to perform a time-consuming task, such
as a disk seek.
- reserved
- Bits,
fields and code values that are set aside for future standardization.
In SCSI, reserved bits should equal zero.
- responder
- The
logical function in an N_Port responsible for supporting
the exchange initiated by the originator in another N_Port.
- ROM
- Read
Only Memory. Data stored in a medium that allows it to be
accessed but not erased or altered.
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