Fibre Channel and Storage Area Networks

Technology backgrounder: what you need to know

Here is a brief summary of Fibre Channel technology and the new architecture that it enables - the Storage Area Network (SAN).

Example Storage Area Network

San Overview

Fibre Channel SANs Compared To LANs/WANs

  • A new acronym: SAN = Storage Area Network
  • SANs connect servers with data storage devices and enable resource sharing between hosts
  • A Fibre Channel SAN does not replace your LAN or WAN - it is complementary SANs combine the high throughput of channels (e.g. SCSI) with the flexibility of networks (e.g. ethernet)
  • LANs & WANs use "heavyweight" protocols such as TCP/IP and IPX
  • SANs use the "lightweight" SCSI-3 protocol, and thus can transport data much more quickly and efficiently
  • SANs are built from components conceptually equivalent to those used in LANs: Host Bus Adapters (HBAs), hubs, switches & routers

Points to note

  • Remember that SCSI stands for Small Computer Systems Interface. The SCSI standard was not designed with high availability, clustering, high performance RAID or disaster recovery in mind.
  • The Fibre Channel ANSI standard was developed more recently, with the benefit of experience with SCSI and an understanding of its limitations. Thus Fibre Channel is designed from the outset to be more reliable, scalable and flexible than SCSI.
  • Note the distinction between SCSI hardware (e.g. cables, terminators, adapter cards etc) and the SCSI protocol/command set. Fibre Channel replaces SCSI hardware, but retains the SCSI-3 protocol (i.e. the command set/software used in Ultra SCSI).
  • The Fibre Channel standard includes both copper and optical fiber cabling. Transceivers that convert between copper and optical Fibre Channel are called Media Interface Adapters (MIAs).
  • SCSI hardware is half duplex, i.e. devices can send or receive data, but cannot do both simultaneously. Fibre Channel is full duplex, i.e. devices can send and receive data simultaneously, which increases total data throughput by up to 2X.

For more technical information, see this detailed comparison of Fibre Channel and SCSI.

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