FC SAN Technology

 1.    Fiber Channel Storage Area Network (FC SAN) [1]

FC SAN is a system that will facilitate a group of servers to access storage devices on the network with the use of FC SAN. It will facilitate high-functioning data transmissions among the servers and storage devices.

FC SAN is a high-speed network which is built with high speed optic cables and serial copper cables. Data transmission speed is up to 16 GB/s. The data is transmitted without dropping any frames. FC SAN option will provide internal or within limits data movement with high-performance infrastructure

 

2.     Benefits of FC SAN : [2]

·        Easily share storage and manage information

·        Each storage device in the SAN is managed by a specific server

·        Fast speed transmission

·        Saving on installation and operating costs

·        high reliability and save data integrity protection

·        Highly scalable, it can be up to 16 million devices in the whole storage system

·        High and stable data backup speed

3.    Building FC SAN [3]

 

Figure 3.1 FC SAN Design

4.    FC SAN Topologies: [4]

-        There are 5 types of FC SAN topologies: Single- Switch Topology, Cascaded and ring topology, Mesh Topology and Core-edge topology, Edge-core-edge topology.

Ø  Single-Switch Topology:

In the single-switch topology, the storage systems and servers only have one switch have been connect together. This topology helps remove FC frames running on the ISLs , so it helps prevent delay of ISL

 

Figure 4.1 Single Switch

Ø  Cascaded and ring topology

 

Figure 4.2 Cascaded topology

 

Figure 4.3 Ring topology

Ø  Mesh Topology : each switch is connected to every other switch, and any computer systems and storage system can be connected with any switch in the area

 

Figure 4.4 Mesh topology

Ø  Core-edge topology: Storage systems are connected to the core tier , and we can add more core and edge switches to expand the area of network storage system

Figure 4.5 Core-edge topology

Ø  Edge-core-edge topology

Figure 4.6 Edge-core-edge topology

5.    Components of FC SAN

There are 3 main components in a FC SAN system which is Network Adapters ,cables ,interconnecting devices:

-        Network Adapters:

o    FC HBAs (Host Bus Adapter) : used to connect to level storage

Figure 5.1 FC HBA

o   Storage system front-end adapters

-        Cables: [5]

o   In short distance use copper cables

o   In long distance use optical fiber

Figure 5.2 Copper cable and Optical fibre

-        Interconnecting devices:

o   FC switches , FC hubs and FC directors

FC Switch : [6]

Figure 5.3 FC Switch

 

FC Hub: [7]

Figure 5.4 FC Hub

FC director: [8]

Figure 5.5 FC Director

6.     FC interconnectivity options

Point to Point: Two nodes can be connected directly with each other. It will provide a committed connection for data communication among the nodes.

FC arbitrated loop (FC-AL): The attached nodes will have a shared loop. The I/O operations are conducted when each of the device maintains connection with each other. In the loop only one of the devices can execute the I/O operation. The performance on the FC-AL is low because each device must wait for the other device to perform the I/O request. As a loop construction FC-AL has to put on to interconnecting devices by precisely attaching the devices through cables forming a ring. A star topology has to be used to connect the FC hubs.  [9]

 

 

 

 

Figure 6.1 Arbitrated Loop [9]

FC-SW: Communication between the nodes happen with the use of switches. It uses either a single FC switch or a network of FC switches which are connected to the nodes. The Interswitch link is a link between the two switches which facilitates the switches to connect to each other to create single large fabric. These will basically help in transferring the traffic from one switch to the other. It has high scalability. When a node is added or removed it does not affect any movement of the traffic between the nodes. [10]

7.     FC port types

Switch Fabric in FC SAN have the following types of ports:

N Port: It is recognized as the node port and its ending point in the fabric. It is usually a system port which is called the FC HBA port or a system that stores data and connects it to the switch.

E Port: The E Port will create the connection between the FC switches. It works as an expansion port.

F Port: The fibre channel fabric node connects to the port which is called as a fabric port.

G Port: Throughout initialization the E port and the F port determines its functions automatically. It’s a common port on the switch that creates the connections on the Nport.  [11]

8.     FC Architecture

The benefit of the FC architecture is that he has advantages of network and channeling the technologies. As it has low protocol expenditures it give high-level performances. It is good for long distances and also has high scalability. It will transfer data through SCSI over the network.

FC SAN communication protocol architecture can be seen in these 5 layers;

                    Figure 8.1 FC Protocol Stack [12]

FC-4 Layer: It is the top most layer in the FCP pile or stack. The interfaces of the applications are decided in what way the Upper Layer protocol will plan the rest of the lower layers. [13]

FC-2 Layer: Organizing of data, structure and FC addressing is taken care by this layer. Routing, managing the flow, service grouping and fabrication of the services is done by this layer. [13]

FC-1 Layer: Encoding and decoding of the data is done at this level. For eg: An 8-bit character is encoded into a 10-bit transmission character. The this character is communicated to the administrative receiver node. Then the 10-bit character is moved to to be decoded in the original 8-bit character. A speed of 10 Gbps or more is used in FC links which uses 64-bit encrypting algorithm. This layer takes care of the transmission of the data via primitive signals indicating the events. It also takes care of recovering the errors and link initialization. [13]

FC-0 Layer: Transmission of the bits, broadcasting and physical crossing point are taken care at the lowest level of the stack. It contains optical and electric constraints for a variety of statistics rates plus cables and connectors specifications are also taken care of. It can use optical and electrical broadcasting. [13]

9.     Link Aggregation

Figure 9.1 Example of Linked Aggregation [12]

-     Link aggregation has two or additional parallel ISL into a solitary rational ISL known as a port-channel which will produce higher output than a single ISL.  The network traffic is shared to optimize the performance of the fabric. The node ports have pairs which will flow methodically via the ISL in the port-channel.  Invalid source specified.

10. Zoning

Figure 10.1 Fibre Channel Zoning [12]

-     Zoning is a function in the FC switch which has groups of segments which are logically set up so that the mode ports within the fabric can communicate with each other. Whenever any changes are made by the name server database information is sent via (RSCN) Registered State Change Notification to all the nodes. It controls the RSCN in the fabric. With the use of RSCN the fabric will send the information to only those nodes where the changes are made. Access control mechanism is done via zoning which is called the LUN masking.

·       Types of Zoning

     WWN Zoning: Its know as world wide names in zoning. It has a big advantage of flexibility. The configuration of the zone does not need to be moved or changed if the administrator moves any nodes to an alternative switch.

 

Port zoning: In port zoning the switch port ID is used. Access is determined by understanding on which switch port the nodes are connected. The port identifiers are the zone representatives to which the FC HBA and its targets which are storage systems are connected.

Mixed zoning: It has a combination of WWN zoning and port zoning. When a mixed zoning is used it will empower a specific node port to be secured to the WWN of an alternative node. 

 

 

 

 

References

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 Bloggers: Manh Nguyen and Anuradha Jagtap

Group Number : 5