Fibre Channel Products for SANs
In this chapter, you will learn about the following Fibre Channel products:
- Host Bus Adapters
- Storage devices
With the growing popularity of storage area networks (SANs), Fibre Channel technology has emerged to the forefront as an effective means of solving storage-related problems that have plagued corporate networks all over the world. A wealth of Fibre Channel products are available, including Host Bus Adapters (HBAs), connectors, switches, hubs, gateways, and Fibre Channel-to-Small Computer System Interface (SCSI) bridges. Along with optical cables, Fibre Channel products enable network administrators and designers to develop solutions to storage problems related to performance, distance, backups and restoration, bandwidth, and security. For example, Fibre Channel switches play an important role in enhancing the performance of database servers by switching data queries and their results much faster. Similarly, switched Fibre Channel hubs provide high-speed access to disk arrays, tape libraries, and Just a Bunch of Disks (JBODs).
To build a successful SAN that fulfills all or most of the requirements of a corporation, you must choose each device of a SAN with care and understanding. Understanding the purpose and the capabilities of each Fibre Channel device will help you make effective choices while designing a SAN.
With the infiltration of SAN and Fibre Channel technology in corporate storage solutions, many vendors have jumped into the field of Fibre Channel devices. You need not restrict yourself to the Fibre Channel products offered by one single vendor. As a SAN designer, an intelligent mix and match of compatible products will help you to implement a cost-effective and high-performance storage solution.
Similar to network interface cards (NICs) that are used in traditional Ethernets, HBAs provide the physical interface between the input/output (I/O) host bus of Fibre Channel devices (such as servers and storage devices) and the underlying Fibre Channel network. In other words, HBAs connect Fibre Channel devices to Fibre Channel links.
Popularly used I/O host buses include IBM's PCI-MCA, HP's HSC, and Sun's SBus. The term PCI-MCA is a combination of two termsPCI (Peripheral Component Interconnect) and MCA (Micro Channel Architecture). PCI-MCA is a 32-bit, high-speed interface between the processor of a computer and the attached peripheral devices and expansion cards. HP's High Speed Connect (HSC) is a high-speed proprietary interface that functions much like PCI. SBus is a 32-bit bus used in Sun's SPARC workstations. SBus facilitates the transactions between the processor and the attached peripheral devices. SBus can also help the processor in identifying the corresponding device drivers of the attached devices.
In addition to acting as the physical interface between the host bus and the underlying Fibre Channel link, other functions of HBAs include the following:
Initialization of Fibre Channel nodes and ports onto the underlying arbitrated loop or Fabric. Similar to NICs, HBAs also provide a hard-coded, 64-bit Node_Name or World-Wide Name (WWN) address and Port_Name or World-Wide Port Name (WWPN) address to the device and its ports. These addresses help the Fabric in identifying a node or a port before the node or port has been initialized by the loop or has attempted a Fabric logon.
For more information on WWN and WWPN, see Chapter 6, "SAN Topologies."
Support to various upper-level protocols (ULPs), such as TCP/IP, SCSI, and so on.
Interpretation of incoming data streams by performing context switching. When context switching is done at the HBA level, a significant amount of switching overhead is reduced.
Context switching is the capability of an HBA to issue and process multiple commands to various SAN storage devices simultaneously to maximize efficiency when accessing data. The entire concept is similar to multitasking. However, the basic difference between multitasking and context switching is that in multitasking, inactive programs continue to run in the background. In contrast, in context switching, any inactive program is suspended until it becomes active again.
8B/10B encoding of data
For detailed information on 8B/10B coding, refer to Chapter 3, "Fibre Channel Basics."
HBAs can differ on the basis of many criteria. These criteria include the following:
Physical links supportedFibre Channel physical links include copper links, single-mode fiber-optic links, or multi-mode fiber-optic links.
Protocols supportedCommonly implemented Fibre Channel protocols include SCSI, IP, FCP-SCSI, IPI-3, and SB-2.
IPI is a high-bandwidth interface between the host computer and its peripheral devices (hard drives, tape drives, optical libraries, and so on) that supports transactions ranging from 3 to 25 Mbps. IPI-3 is the latest version of IPI. Based on the Single Byte Command Code Set (SBCCS), Single Byte-2 (SB-2) is a signaling protocol that provides high-bandwidth and high-performance communication between the processor and I/O devices. In addition, SB-2 also facilitates long-distance data exchanges.
Operating systems supportedUNIX, Windows NT, AIX, and Macintosh are some of the operating systems that are commonly used in storage environment.
Topologies supportedPoint-to-point, Fibre Channel-Arbitrated Loop (FC-AL), and switched Fabric are the three Fibre Channel topologies.
Number of connections supportedConnections can be single node to Fibre Channel link connections, multiple connections, or multiple switched connections.
For detailed information on the three topologies mentioned in the preceding list, see Chapter 6.
With an increase in the number of vendors manufacturing Fibre Channel products, SANs are growing heterogeneous in nature. This implies that SANs are using more and more varied hardware and software platforms. Therefore, of the many HBAs that are available today, it is very important to choose HBAs that can support a wide variety of platforms.
Several vendors offer a variety of HBAs. IBM, JNI Corp., Qlogic, and HP are some of the more popular HBA vendors. The price of an HBA can range from $500 to $1500 per adapter. Figure 4-1 shows an HBA.
Figure 4-1 HBA