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Storage Networking (FC, iSCSi, FCoE)


Fibre Channel (FC) is a technology for transmitting data between computer devices at data rates of up to 20 Gbps at present time and more in the near future.

Fibre Channel began in the late 1980s as part of the IPI (Intelligent Peripheral Interface) Enhanced Physical Project to increase the capabilities of the IPI protocol. That effort widened to investigate other interface protocols as candidates for augmentation. In 1998, Fiber Channel was approved as a project and now have become and industry standard.

iSCSI - Internet Small Computer System Interface, is a storage networking standard used to link different storage facilities.

iSCSI is used to transmit data over local area networks, wide area networks or the Internet and can enable location-independent data storage and retrieval and is one of two main approaches to storage data transmission over IP networks.

The other method, Fibre Channel over IP, translates Fibre Channel control codes and data into IP packets for transmission between geographically distant Fibre Channel SANs.

User Benefits

Fibre Channeldelivers cost-effective solutions for storage and networks, provides versatile connectivity with scalable performance, it support multiple topologies like dedicated point-to-point, shared loops, and scaled switched topologies meet application requirements. It provides full duplex operation with separate transmit and receive fibers. Despite the name, Fibre Channel can run over both copper and fiber media.

It is a scalable and high efficient technology. From single point-to-point gigabit links to integrated enterprises with hundreds of servers, Fibre Channel delivers unmatched performance. Fibre Channel protocol, is specifically designed for highly efficient operation using hardware means that delivers data as fast as the destination buffer is able to receive it.

The iSCSI protocolprovides numerous benefits for SANs. A few key points are summarized below:

  • iSCSI uses traditional networking standards: Ethernet and TCP/IP. Most IT administrators are already familiar with TCP/IP, unlike the more complex skills required for FC storage.
  • Total storage costs are reduced: iSCSI SANs are easier to install and maintain, lowering installation and maintenance expenses.
  • Replication works over a standard IP network: iSCSI replication eliminates distance limitations and costs associated with FC routers.
  • Reduces complexity by eliminating Fibre Channel switches and cabling: Using standard Ethernet switches simplifies everything as most organizations already have in house IP networking skills.
  • iSCSI is the most cost effective storage solution for SMBs: iSCSI offers simplified management and integration based on existing infrastructure and eliminates the need to buy expensive equipment.
  • Works over longs distance: iSCSI solves the issues of distance and bandwidth. The use of IP Networking means long distance is no longer an issue for replicating to remote sites.
  • iSCSI standard has been supported by Microsoft, IBM, Cisco, Intel, and many others with the ratified standards by the Internet Engineering Task Force (IETF).
  • iSCSI is a scalable technology

Business Impact

Fibre Channel can be implemented in three topologies to interconnect varying numbers of devices, called nodes in Fibre Channel terminology. The topologies are point-topoint, arbitrated loop, and crosspoint switched, or fabric (a Fibre Channel term for a network of one or more switches connecting multiple nodes).

Fibre Channel is making the biggest impact in the storage arena, in particular, using SCSI as an upper layer protocol. Compared with traditional SCSI, the benefits of mapping the SCSI command set onto Fibre Channel include:

  • faster speed
  • more devices can be connected together
  • larger distance allowed between devices

Being able to access mass storage devices quicker and from greater distances is very attractive to such applications as multimedia, medical imaging, and scientific visualization. Because of the greater distances allowed, Fibre Channel has advantages in disaster recover situations as storage devices can be placed remotely.

Another advantage of Fibre Channel is that it uses small connectors. The serial connectors used for Fibre Channel are a fraction of the size of SCSI parallel connectors and have fewer pins, thereby reducing the likelihood of physical damage. Also, depending on the topology, many more devices can be interconnected on Fibre Channel than on existing channels

Since iSCSIuses traditional networking standards, is easy to implement and maintain and there is no need to hire or outsource storage administration.

When it come about storage, on organization must separate traffic, either physically or logically, from the ordinary LAN traffic to run the network efficiently because the storage system shouldn’t have to compete for bandwidth. Isolating the storage traffic will help to improve response times, prevent bottlenecks, nip potential performance issues in the bud and build in security.

Beyond the best practice of separating the storage traffic, other best practices for operating iSCSI SANs include:

iSCSI SAN redundancy. Choose a storage array that is fully redundant with no single points of failure; it should support multiple spare disks and automatic rebuilds and non disruptive upgrades of hardware and software.

Security for the management tools. This can be done by granting access to the storage system only to authorized employees.

Administrators need to make sure that only the desired servers can access the designated target storage

Use performance analytics tools. Examining server’s workloads and measuring the performance can help determine which network architecture is best fit.

Products supporting this technology

Fibre Channel.

There are three major Fibre Channel topologies: Point-to-Point, Arbitrated loop, Switched fabric

Point-to-Point. Two devices are connected directly to each other. Fibre channel devices communicate at full bandwidth.

Arbitrated loop. All devices are in a loop or ring, similar to token ring networking. Adding or removing a device from the loop causes all activity on the loop to be interrupted. The failure of one device causes a break in the ring. Fibre Channel hubs exist to connect multiple devices together and may bypass failed ports. A loop may also be made by cabling each port to the next in a ring.

All devices share the bandwidth, and only two can communicate with each other at the same time, with each node repeating the data to its adjacent node.

Switched fabric. All devices or loops of devices are connected to Fibre Channel switches, similar conceptually to modern Ethernet implementations. A switch fabric is the most flexible topology, enabling all servers and storage devices to communicate with each other. It also provides for a failover architecture in the event a server or disk array ceases to operate.

Fibre Channel infrastructure consists of switches and HBA adapters.

Most switch manufacturers offer a variety of interoperability modes above and beyond the native and open fabric states. These native interoperability modes allow switches to operate in the native mode of another vendor and still maintain some of the proprietary behaviors of both. However, running in native interoperability mode may still disable some proprietary features and can produce fabrics of questionable stability.

Fibre Channel HBAs are available for all major open systems, and each HBA has a unique World Wide Name, which is similar to an Ethernet MAC address