IBM TotalStorage 2109 M12, User Manual

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public NL_port. A node loop port (NL_port) that logs
into the fabric, can function within either a public or
private loop, and can communicate with either private or
public NL_ports.
Q
quad. A group of four adjacent ports that share a
common pool of frame buffers.
QuickLoop. (1) A feature that makes it possible to
allow private devices within loops to communicate with
public and private devices across the fabric through the
creation of a larger loop. (2) The arbitrated loop created
using this software. A QuickLoop can contain a number
of devices or looplets; all devices in the same
QuickLoop share a single arbitrated loop physical
address (AL_PA) space.
QuickLoop mode. A hardware translative mode that
allows private devices to communicate with other private
devices across the fabric. See also hardware translative
mode and standard translative mode .
R
RAID. See redundant array of independent disks .
RAM. See random access memory .
RAN. Remote Asynchronous Notification.
random access memory (RAM). A temporary storage
location in which the central processing unit (CPU)
stores and executes its processes.
R_A_TOV. See resource allocation timeout value .
read only memory (ROM). Memory in which stored
data cannot be changed by the user except under
special conditions.
receiver ready (R_RDY). A primitive signal indicating
that the port is ready to receive a frame.
reduced instruction set computer (RISC). A
computer that uses a small, simplified set of frequently
used instructions for rapid processing.
redundant array of independent disks (RAID). A
collection of disk drives that appear as a single volume
to the server and are fault tolerant through mirroring or
parity checking.
registered state change notification (RSCN). A
switch function that allows notification of fabric changes
to be sent from the switch to specified nodes.
remote fabric. A fabric that spans across wide area
networks (WANs) by using protocol translation (a
process also known as tunneling) such as fibre channel
over asynchronous transfer mode (ATM) or fibre
channel over Internet protocol (IP).
remote procedure call (RPC). A facility that a client
uses to request the execution of a procedure call from a
server.
Remote Switch. A feature that runs on Fabric
operating system (OS) and enables two fabric switches
to be connected over an asynchronous transfer mode
(ATM) connection. This requires a compatible Fibre
Channel to ATM gateway, and can have a distance of
up to 10 km (6.214 mi) between each switch and the
respective ATM gateway.
request rate. The rate at which requests arrive at a
servicing entity. See also service rate .
resilient core. A single fabric that uses two or more
switches as a core to interconnect multiple edge
switches. Synonymous with dual-core fabric.
resource allocation timeout value (R_A_TOV). Used
to time out operations that depend on the maximum
possible time that a frame can be delayed in a fabric
and still be delivered. This value is adjustable in one
microsecond increments from 10—120 seconds.
resource recover timeout value (RR_TOV). The
minimum time a target device in a loop waits after a
loop initialization primitive (LIP) before logging out a
small computer systems interface (SCSI) initiator. See
also error detect timeout value and resource allocation
timeout value .
RISC. See reduced instruction set computer .
RLS probing. Read link status of the arbitrated loop
physical addresses (AL_PAs).
ro. Read only.
ROM. See read only memory .
route. As applies to a fabric, the communication path
between two switches. Can also apply to the specific
path taken by an individual frame, from source to
destination. See also Fibre Channel shortest path first .
routing. The assignment of frames to specific switch
ports, according to frame destination.
RPC. See remote procedure call .
R_RDY. See receiver ready .
RR_TOV. See resource recovery timeout value .
RS-232 port. A port that conforms to a set of Electrical
Industries Association (EIA) standards. Used to connect
data terminal equipment (DTE) and data
communications equipment (DCE) devices for
Glossary
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