This chapter provides a brief overview of Fibre Channel with regard to SGI Fibre Channel options. It briefly explains the following:
For more information, see the following resources:
ANSI Fibre Channel standards: Global Engineering Documents, 15 Inverness Way East, Englewood, CO, 80112, USA. Telephone: +303 397 0271 or 1 800 854 7179 (U.S. and Canada)
Fibre Channel Industry Association (FCIA): http://www.fibrechannel.org
Storage Networking Industry Association (SNIA): http://www.snia.org/home
Note: Some information in this chapter was derived from the Fibre Channel Loop Community (FCLC) website, and the Fibre Channel Association (FCA) technical information website.
Fibre Channel is the general name of an integrated set of standards being developed by the American National Standards Institute (ANSI). The Fibre Channel standard defines a high-speed data transfer interface that can be used to connect workstations, mainframes, supercomputers, storage devices, and displays. The Fibre Channel standard addresses the need for very fast transfer of large amounts of information. Currently, Fibre Channel is used primarily as an interface to storage.
Conceived as a generic, efficient physical transport system that can support multiple protocols, the standard also relieves system manufacturers of the burden of supporting the various channels and networks currently in place, because it provides one standard for networking, storage, and data transfer. Note that this SGI implementation is for communication with mass storage systems only.
Fibre Channel can provide a general transport vehicle for Upper Level Protocols (ULPs), including the Intelligent Peripheral Interface (IPI) and Small Computer System Interface (SCSI) command sets, high-performance parallel interface (HIPPI) data framing, Internet Protocol (IP), and IEEE 802.2. Proprietary and other command sets can also use and share the Fibre Channel, although such use is not defined as part of the Fibre Channel standard and is not supported by SGI host systems. The SGI implementation currently supports only the SCSI Fibre Channel protocol.
| Note: For a description of SGI Fibre Channel storage options, see SGI TP9300 RAID Owner's Guide (007-4644-001 or later), SGI TP9400 and SGI TP9500 RAID Owner's Guide (007-4304-001 or later), SGI Total Performance 9100 Storage System Owner's Guide (007-4068-003 or later), or Origin FibreVault and Fibre Channel RAID Owner's Guide (007-3428-004 or later). |
The two most common peripheral protocols for device communication in the computer industry are networks and channels.
Networks have the following characteristics:
Involve I/O interfaces that usually support many small transactions with relatively high overhead due to software involvement in the flow of information.
Allow a host or device in the network to communicate with any other device.
Operate in an open, unstructured, and unpredictable environment.
Channels have the following characteristics:
Supply peripheral I/O interface to a host and transport large amounts of data between the host and peripherals.
Keep data processing overhead to a minimum by handling data transfer in hardware, with little or no software involvement once an I/O operation begins.
Operate in a closed, structured, and predictable environment where all devices that can communicate with a host are known in advance and any change requires host software or configuration table changes.
Fibre Channel technology attempts to combine the best of these two methods into an I/O interface that meets the needs of both channel users and network users. Fibre Channel communications can be conducted over copper twinax, twisted pair, or optical fiber.
Fibre Channel technology provides different interconnect topologies to serve the combined needs of channel and network usages. These topologies are the following:
Fabric
Arbitrated loop, including point-to-point
Currently, SGI supports both these topologies.
A fabric is an active, intelligent interconnect scheme for Fibre Channel servers and storage. Fabric topology permits dynamic interconnections between nodes through ports connected to the fabric.
A Fibre Channel switch is the cornerstone of the fabric, supporting connectivity of a range of host and storage types. Switches can be cascaded for more complex configurations. Parallel fabrics can provide redundancy. SGI provides 8-port, 16-port, 32-port, and 64-port switches with a variety of cabling options. See “Connections for SGI Fibre Channel Options” in Chapter 3 for details of connections.
In Fibre Channel arbitrated loop (FC-AL) topology, each port arbitrates for access to the loop. Ports that “lose” the arbitration act as repeaters of all traffic on the loop. The loop is a dedicated transmit channel and a dedicated receive channel that are clad together into one cable to form a loop out and back. This protocol allows as many as 127 ports to be connected in a serial loop (one FL_Port and 126 NL_Ports). SGI supports a maximum of 110 disks in a single rack.
Ports are called Node Ports (N_Ports), Node_Loop Ports (NL_Ports), Fabric_Ports (F_Ports), or Fabric_Loop Ports (FL_Ports).
An NL_Port represents each disk in a disk array. Each NL_Port sees all messages and passes messages not addressed to that port. Ports passing messages are said to be in “repeat mode.”
The SGI Fibre Channel hub, an intelligent digital hub for FC-AL storage clusters, provides gigabit-speed storage connectivity, network management, data reliability, and module network scalability for SGI storage configurations. The hub uses copper cabling, and optical cabling with media interface adapters (MIAs). Its ten FC-AL ports can function as a single loop, can be segmented into two 5-port loops, or can be connected (cascaded) with another SGI Fibre Channel hub to form one 18-port loop.
Figure 2-1 shows Fibre Channel in the overall Origin 2000 and Onyx2 I/O structure.
Fibre Channel is useful for many applications, including the following:
Scientific graphics and video markets, which use high-bandwidth rates with large I/O requests.
Fileserver and database markets, which must support many I/Os per second (IOPS) with relatively small random I/Os.
High-availability RAID is also a requirement for this market. Fibre Channel RAID addresses the needs of this market by supporting several disks in a well-balanced access pattern on a single arbitrated loop. The arbitrated loop also provides an arbitration fairness scheme that prevents high-priority requests from starving low-priority requests. For more information on high availability and RAID within Fibre Channel options, see SGI TP9300 RAID Owner's Guide (007-4644-001 or later), SGI TP9400 and SGI TP9500 RAID Owner's Guide (007-4304-001 or later), SGI Total Performance 9100 Storage System Owner's Guide (007-4068-003 or later), or Origin FibreVault and Fibre Channel RAID Owner's Guide (007-3428-004 or later).