18 Copyright 2012 EMC Corporation All rights reserved Module 5 Fibre Channel

18 copyright 2012 emc corporation all rights reserved

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18 Copyright © 2012 EMC Corporation. All rights reserved
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Module 5: Fibre Channel Storage Area Network Traditionally, host computer operating systems have communicated with peripheral devices over channel connections, such as a ESCON and SCSI. Channel technologies provide high levels of performance with low protocol overheads. Such performance is achievable due to the static nature of channels and the high level of hardware and software integration provided by the channel technologies. However, these technologies suffer from inherent limitations in terms of the number of devices that can be connected and the distance between these devices. In contrast to channel technology, network technologies are more flexible and provide greater distance capabilities. Network connectivity provides greater scalability and uses shared bandwidth for communication. This flexibility results in greater protocol overhead and reduced performance. The FC architecture represents true channel/network integration and captures some of the benefits of both channel and network technology. It provides both channel speed for data transfer with low protocol overhead and scalability of network technology. The Fibre channel protocol (FCP) forms the fundamental construct of the FC SAN infrastructure. FCP is the implementation of serial SCSI-3 over an FC network. In FCP architecture, all external and remote storage devices attached to the SAN appear as local devices to the host operating system. The key advantages of FCP are as follows: Sustained transmission bandwidth over long distances Support for a larger number of addressable devices over a network. Theoretically, FC can support over 15 million device addresses on a network Support speed up to 16 Gbps (16 GFC) 19 Copyright © 2012 EMC Corporation. All rights reserved
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Module 5: Fibre Channel Storage Area Network It is easier to understand a communication protocol by viewing it as a structure of independent layers. FCP defines the communication protocol in five layers: FC-0 through FC-4 (except FC-3 layer, which is not implemented). FC-4 Layer: It is the uppermost layer in the FCP stack. This layer defines the application interfaces and the way Upper Layer Protocols (ULPs) are mapped to the lower FC layers. The FC standard defines several protocols that can operate on the FC-4 layer (see Figure 5-11). Some of the protocols include Small Computer System Interface (SCSI), High Performance Parallel Interface (HIPPI) Framing Protocol, Enterprise Storage Connectivity (ESCON), Asynchronous Transfer Mode (ATM), and IP. FC-2 Layer: It provides Fibre Channel addressing, structure, and organization of data (frames, sequences, and exchanges). It also defines fabric services, classes of service, flow control, and routing. FC-1 Layer: It defines how data is encoded prior to transmission and decoded upon receipt.
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