Fiber Channel switch
A network switch compatible with the Fiber
Channel protocol. Allows the creation of a Fiber
Channel network, which is currently the core
component of most storage area networks
(SANs).
Fiber Channel topology
The method of connecting Fiber Channel ports
together. A point-to-point (P2P) topology
connects two devices directly to each other, with
no hub or switch in between. A loop topology
usually connects two or more devices in a ring,
but can also connect two devices directly to
each other just like a P2P topology can. A full-
fabric topology connects multiple devices in a
network.
firewall
A device or set of devices, either hardware- or
software-based, designed to permit or deny
network transmissions based upon a set of rules.
Used to protect networks from unauthorized
access while permitting legitimate
communications to pass. Many personal
computer operating systems include software-
based firewalls to protect against threats from
the public Internet.
firmware
Small, fixed software applications, stored in
read-only memory (ROM) or programmable read-
only memory (PROM), that internally control
various electronic devices. In Nexsan storage
systems, each RAID controller is loaded with
firmware to control its functionality.
Occasionally, this firmware must be updated
using the Update Firmware page in the graphical
user interface.
frame
A data packet on an Ethernet or Fiber Channel
link. Each frame encapsulates a piece of data
with sender and destination information, along
with a data integrity check routine. Normal
frames can contain data up to 1,500 bytes in
length. Jumbo frames can contain larger data
payloads (9,000 bytes on Nexsan storage
systems) and are supported on 1Gb/s and
10Gb/s Ethernet (10GbE) networks. Jumbo
frames are typically used to boost performance
of iSCSI traffic.
FUA
Force Unit Access. A bit in some SCSI
commands which forces a storage device to
bypass cache memory and directly access the
storage medium.
full duplex
See “duplex”.
G
gateway
An internetworking system that joins together the
different subnets of a network or two networks
that use different base protocols. A network
gateway can be implemented completely in
software, completely in hardware, or as a
combination of both.
Gb
Gigabit. Approximately one billion
(1,000,000,000) bits.
GB
Gigabyte. Approximately one billion
(1,000,000,000) bytes. Used to describe the
storage capacity of hard disk drives. A gigabyte
is usually computed as 10^9 (1,000,000,000)
bytes, but can also be computed as 2^30
(1,073,741,824) bytes (often called a “binary
gigabyte” and abbreviated GiB).
Gb/s
Gigabits (Gb) per second. Used to describe the
speed of network data transmission.
GB/s
Gigabytes (GB) per second. Used to describe
the speed of network data transmission. 1 GB/s
is eight times faster than 1Gb/s.
GBIC
See “gigabit interface converter”.
Glossary
Nexsan High-Density Storage
User Guide
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