Storage Area Networks For Dummies®

Chapter 2: SAN Building Blocks
29
✓ LC connectors are smaller, second-generation connectors used in SANs
that operate at the faster speeds of 2 Gbps (equal to 200 megabytes per
second), 4 Gbps (equal to 400 megabytes per second), 8 Gbps (equal to
800 megabytes per second, and 10 Gbps (equal to 1000 megabytes per
second, or a gigabyte per second.)
When the term Gbit is used to refer to data-transfer speed, it means the
same as the standard unit of measurement Gbps (gigabits, or billions of
bits per second). Now, that’s a lot of bits to move in a single second!
The Fabric Layer
Common devices found in the fabric layer of a SAN can include SAN hubs, SAN
switches, data routers, protocol bridges, gateway devices, and cables. The
fabric layer is the actual, tangible network part of the SAN: All the stuff in the
fabric layer of a storage network moves data — usually from an initiator (a
source component, typically the HBA port in a server) to a target (a receiving
component, typically a port on a storage device).
Understanding storage fabrics
Even a simple word like fabric takes on more than one meaning in the world
of SANs:
✓ The fabric layer (“the fabric” for short) is storage geek-speak for the
hardware in a traditional storage area network, specifically one that
uses Fibre Channel components and storage.
✓ A storage fabric is a set of organized, connected storage devices on a
network of interconnected switches that can be accessed by servers. A
storage fabric is created when one or more Fibre Channel switches (as
many as 239) are connected and used in a SAN.
✓ A switched fabric consists of all the switches in a single storage fabric.
✓ A SAN fabric consists of all the individual switched fabrics in a SAN.
A SAN can have more than one switch, and more than one fabric; in fact, most
use at least two fabrics for redundancy. A single switch can be the only switch
in a fabric, or a single fabric can have many connected switches. When switches
are not connected together, they constitute individual fabrics, and even get their
own fabric IDs (identifying numbers set inside each switch).