1. What is Fibre Channel? What is Fibre Channel? Introduction
This lesson examines the relationship between Fibre Channel (FC) and Storage Area Networks (SANs), introduces some of the basic characteristics of FC, and explains why these characteristics make FC well-suited for storage networking.
Importance
FC is similar in many respects to other data networks, but it also has characteristics of the I/O channel architecture that has traditionally been used to connect storage devices to servers. Understanding the characteristics of FC will help you better understand and articulate how FC solutions are able to meet your customer’s needs.

2. Lesson Objective
Upon completion of this lesson, you will be able to describe the key characteristics of Fibre Channel.
Performance Objective
Upon completion of this lesson, you will be able to describe the key characteristics of FC.
Enabling Objectives
Describe FC as a data transport technology that is well-suited to storage networks
Describe the relationship between FC and SANs
List the advantages of FC for SANs
List the features of traditional I/O channels
List the features of traditional data networks
Compare FC to traditional I/O buses and data networks

3. Outline What is Fibre Channel? Fibre Channel and SANs
Advantages of Fibre Channel for SANs
Traditional I/O Channels
Traditional Data Networks
Fibre Channel: The Best of Both Worlds
Prerequisites
All previous lessons in Curriculum Unit 2, Module 1.

4. LAN SAN What is Fibre Channel?
Fibre Channel is a technology for transporting data between devices
Fibre Channel is the transport technology most commonly used for SANs today FC FC FC
What is Fibre Channel?
Objective
Describe FC as a data transport technology that is well-suited to storage networks
Introduction
This section describes FC as a data transport technology.
Definition
FC is a technology for transporting data between devices. It is the network interconnect technology that is most commonly used for SANs today.
Facts
Traditional storage technologies, such as SCSI, are designed for controlled, local environments. They support few devices and only short distances, but they deliver data quickly and reliably. Traditional data network technologies, such as Ethernet, are designed for chaotic, distributed environments. They support many devices and long distances, but delivery of data can be delayed.
FC combines the best of both worlds. It supports many devices and longer distances, and it provides reliable data delivery
Example
In the diagram, the network on the right, consisting of servers and storage devices, is an FC SAN. The SAN consists of servers and storage devices connected by an FC network. FC
IP Network
Fibre Channel Fabric FC FC
LAN
SAN

5. Fibre Channel and SANs “Fibre Channel” and “SAN” are not synonymous:
There are other SAN networking technologies
Fibre Channel has been applied to other applications
Today:
Most SANs are built on Fibre Channel
Fibre Channel is most commonly used to build SANs
Fibre Channel and SANs
Objective
Describe the relationship between FC and SANs
Introduction
This section describes the relationship between FC technology and SAN implementations.
Facts
FC is a data transport technology that is frequently used in SANs.“Fibre Channel” and “SAN” are not synonymous. FC is not exclusively a SAN networking technology, nor is it the only SAN networking technology:
Other technologies besides FC are used to build SANs, including IBM’s Enterprise Systems Connection (ESCON) and Fibre Connection (FICON) technologies, High Performance Parallel Interface (HiPPI), and IP storage technologies.
FC has been applied to applications other than storage, including specialized applications such as video broadcast and avionics applications.
Today, most SANs are built on FC, and FC is most commonly used to build SANs. That may not be the case tomorrow. Emerging IP storage technologies, such as Internet SCSI (iSCSI), will both complement and compete with FC.

6. Advantages of Fibre Channel
High bandwidth (2Gb/s today, 10Gb/s soon)
Long distances
Many devices
Many protocols and applications
Proven and reliable
Open standards
Fibre Channel
Advantages of Fibre Channel for SANs
Objective
List the advantages of FC for SANs
Introduction
This section lists the advantages of FC technology for SAN implementations.
Facts
Certain performance characteristics of FC have caused it to become the dominant SAN foundation technology:
It provides high bandwidth—1 Gb/s since 1995 and 2 Gb/s since 2001; the 10 Gb/s specification is scheduled for completion in 2003.
It supports long distances—up to 10 Km per link, instead of SCSI’s dozens of meters.
It supports many devices—about 16 million addressable nodes, versus 8 or 16 devices per SCSI bus.
It supports many protocols and applications, and is compatible with most existing storage applications.
It is a proven and reliable technology.
It is based on open standards, allowing many vendors to compete to produce the best products. Support for open standards has helped gain FC support from the entire storage marketplace.

7. I/O Channels I/O Channel (SCSI) Few devices Static Low latency
Short distances
Hardware-based delivery management
I/O Channels
Objective
List the features of traditional I/O channels
Introduction
This section describes the characteristics of traditional I/O channels.
Facts
To understand why FC has been so successful in the storage networking market, a designer needs to understand how it differs from other storage I/O buses—sometimes known as I/O channels—and data networks.
What is an I/O channel?
A channel is a directly attached and well-structured mechanism designed to transmit data between a host and a small number of devices in a well-known configuration. Devices generally cannot be added to a channel without disrupting existing communication sessions.
Because channels are static and well-structured, data can be routed between devices with minimal delays, providing low latency.
Channels generally use a parallel architecture. This architecture can support high speeds, but only short distances.
Due to the static and well-structured nature of channels, they perform only minimal decision-making tasks. These tasks can be performed by hardware, which ensures a minimal load on the host’s CPU and provides rapid delivery of data.
The preceding graphic uses a SCSI connection as an example of a channel. The advantages of SCSI technology are designated with green check marks, while a red X marks each of the limitations of SCSI technology.

8. Data Networks I/O Channel (SCSI) Network (Ethernet) Few devices
Static
Low latency
Short distances
Hardware-based delivery management
Many devices
Dynamic
High latency
Long distances
Software-based delivery management
Data Networks
Objective
List the features of traditional data networks
Introduction
This section describes the characteristics of traditional data networks.
Facts
What is a network?
Networks are designed to dynamically adjust to changing environments in which the number and configuration of devices on the network are expected to change. Devices can be added to a network without disrupting existing communication sessions.
Because networks route data through complex and changing paths, end-to-end latency can be significantly higher than in a channel.
Networks generally use a serial architecture, which supports both high speeds and long distances.
In a network, more decision-making tasks must be performed on-the-fly in order to route data through the network. These tasks are performed mainly by software running on each host, consuming CPU cycles on each host and delaying the delivery of the data.
The preceding graphic shows an Ethernet network on the right. The advantages of Ethernet are marked with green check marks, while limitations are indicated with a red X.

9. Fibre Channel: The Best of Both Worlds
I/O Channel
Fibre Channel
Network
Few devices
Static
Low latency
Short distances
Hardware-based delivery management
Many devices
Dynamic
Low latency
Long distances
Hardware-based delivery management
Many devices
Dynamic
High latency
Long distances
Software-based delivery management
Fibre Channel: The Best of Both Worlds
Objective
Compare FC to traditional I/O buses and data networks.
Introduction
This section compares FC capabilities to traditional I/O buses and data networks.
Facts
FC is designed to incorporate the best features of both channel and network architectures:
FC’s serial architecture allows it to support many devices and flexible configurations.
Like a network, FC is designed to dynamically adjust to changing environments. For example, FC allows devices to be added to the SAN with minimal disruption to ongoing communication sessions.
Storage networks are generally somewhat simpler and more “stable” than data networks (such as the Internet). Therefore, FC compromises between flexibility and efficiency in order to minimize end-to-end latency.
FC’s serial architecture supports long distances at high speeds.
FC HBAs incorporate application-specific integrated circuits (ASICs) that perform delivery management services in hardware, minimizing host CPU load and further reducing latency.

10. Lesson Review
Identify the disadvantages of channels and networks:
Channels
Networks
Not scalable 
Inflexible 
Practice
1. Identify the disadvantages of traditional I/O channels and data networks by matching each of the listed characteristics to either channels or networks.
High latency 
Limited distance 
High CPU loads 

11. Lesson Review (cont.)
Match Fibre Channel’s characteristics to the features that enable those characteristics:
____ Long distances
____ Low latency
____ Many devices
____ Minimal CPU load
____ Scalability a
Serial architecture
Hardware-based delivery management
Dynamic configuration b
a,c b
2. Match Fibre Channel’s characteristics to the features that enable those characteristics.
___ Long distances
___ Low latency
___ Many devices
___ Minimal CPU load
___ Scalability
a,b,c
Serial architecture
Hardware-based delivery management
Structured data paths

12. Summary Fibre Channel is a technology for transporting data
“Fibre Channel” and “SAN” are not synonymous
Fibre Channel has evolved to become the dominant SAN foundation technology because it supports high bandwidth, long distances, many devices, and multiple applications, and because it is based on open standards
Traditional I/O channels offer low latency, but they support limited distances and numbers of devices
Traditional data networks are fast and support long distances, but they suffer from high latency and CPU utilization
Fibre Channel is ideal for storage networks because it supports many devices, low latency, long distances, and hardware-based delivery management
Summary: What is Fibre Channel?
In this lesson, you learned to describe FC as a data transport technology suitable for storage networks, explain the relationship between FC and SANs, and compare FC to other I//O buses and data networks.