|Communicator e3000 MPE/iX Release 7.5 (Software Release C75.00): HP e3000 MPE/iX Computer Systems
> Chapter 4 Fibre Channel Device and Adapter Support
Fibre Channel Device Adapter Support
With MPE/iX Release 7.5, support has been introduced for new Fibre Channel Device Adapter cards on N-Class and A-Class HP e3000 systems. These PCI-bus based adapter cards provide the ability to connect a Fibre Channel device directly to the HP e3000 system using Fibre channel cables. Prior to MPE/iX 7.5, HP e3000 systems supported connectivity to fibre channel devices only through a SCSI-Fibre Channel Router connected on a PCI-SCSI HVD card or NIO FW-SCSI card. Now with the support for Fibre Channel (FC) adapter cards, the router is no longer needed for N- and A-class systems. The Fibre Channel adapter cards require new software and new SYSGEN configuration values. The purpose of this article is to provide an external "System Administrator" view of these changes in MPE/iX. The opening section of the article describes the motive for supporting FC adapter cards. The next section gives details of the new FC Device Adapter cards supported. The third section is a review of Fibre Channel Concepts (which you may want to read first if all of this is new to you). The configuration of Fibre Channel adapter cards and attached FC devices using SYSGEN is covered in a separate article in this Communicator.
SCSI-FC Router vs. Fibre Channel Adapter
Prior to MPE/iX 7.5, fibre channel devices could be connected to N- and A-class HP e3000 systems only through a SCSI-FC Router (A5814A-003). This router is a protocol converter between SCSI and Fibre Channel. The SCSI-FC Router has one Ultra SCSI-HVD port and one Fibre Channel port. So a SCSI adapter card on an HP e3000 can be connected to the SCSI-FC Router through a SCSI cable. On the other end of the router, a FC cable connects to the FC device. This arrangement allows the HP e3000 system to access the FC device through the router. Figure 4-1 Accessing FC Device through SCSI-FC Router
Although this setup provided the capability for HP e3000 customers to connect FC devices, this arrangement has multiple components and hence not easy to maintain. Since there are multiple connections, there can be multiple points of failure possible. If there is a fault, it is necessary to individually check the SCSI adapter card, SCSI cable, SCSI-FC router, FC cable and the FC device to see where the problem is. Thus using the SCSI-FC router to access FC devices introduces multiple points of failure. Moreover accessing FC devices through the router and SCSI cable brings down the high FC transfer rates ultimately to lower SCSI transfer rates. Thus the FC storage devices are not getting used to their full performance capability. Also a "SCSI view" of the FC device provided by the router limits the number of Logical Units (LUNs) that can be effectively used by the host system. SCSI-FC router can be viewed more as a quick and easier way of allowing fibre channel connectivity for HP e3000 systems. But this will not be able to meet the fibre channel storage needs of HP e3000 customers for long. Figure 4-2 Accessing FC Device through FC Device Adapter
In order to allow HP e3000 customers to take full advantage of FC storage devices and also ease maintenance issues, MPE/iX 7.5 introduces the support of native Fibre Channel adapter cards. These adapter cards can be used in the PCI I/O slots of N/A-Class systems and can connect directly to the FC devices through an FC cable, thus providing higher I/O performance and simpler connectivity. It is to be noted that fibre channel device adapter cards are supported only on N-Class and A-Class HP e3000 systems. Other HP e3000 models like 99x and 9x9 systems would continue to need the SCSI-FC router for connecting to fibre channel devices.
Benefits to Customers
The introduction of support for FC device adapter cards brings the following benefits to HP e3000 customers:
Fibre Channel Adapter Card Supported
The Fibre Channel Device Adapter Card available for N- and A-Class Systems is:
Fibre Channel Concepts
Fibre Channel BasicsA fibre channel environment or network consists of host systems and devices connected together by an interconnection topology. In fibre channel terminology, both host systems and devices are referred to as nodes. Each node is a source or destination of information for one or more other nodes. Each node requires one or more ports to provide a physical interface for communicating with other nodes via their ports. The port is a hardware attachment that allows the node to send and receive information via the physical interface. Ports may be integrated into the device or packaged as a separate pluggable card. Many peripheral devices such as disk or tape drives use integrated ports while most host systems use pluggable Host Bus Adapter (HBA) ports for flexibility. Fibre channel protocol allows transporting of upper layer protocols like SCSI command set over it, thus enabling it to be used for connecting mass storage devices. Each fibre channel node contains at least one hardware interface port that connects the node to the topology and transports information to or from other ports. This port is referred to as a node port or N_Port for short. A node may have a single N_Port or multiple N_Ports. Each N_Port has a Port_Name, which is a unique 64-bit identifier assigned to the port at the time of manufacture or installation. Since no two ports in the world are assigned the same name, it results in a unique "World-Wide Name" (WWN). Each N_Port also has one or more 24-bit address identifiers called the N_Port ID, which is used to address the node within a topology and route information to it. Ports are connected together through an interface topology. The topology consists of the physical interface and interconnection scheme. The physical interface determines the signaling rate and communication distances. It defines transmission mechanisms such as optical of electrical signaling and specifies the cables and connectors used by that interface. The topology defines the interconnection scheme. It determines how many nodes can be connected together, how information is routed among the nodes, total bandwidth available and delivery latencies.
Fibre Channel TopologiesFibre Channel allows three different types of topologies for interconnecting nodes. They are:
Since a fabric topology is complex and costlier, fibre channel technology allows FC devices to be connected in a rather simpler topology called the Arbitrated Loop or Private Loop topology. A private loop is just a ring-like connection of FC devices and host systems, with each entity physically connected only to its adjacent one on either side. It forms a loop because communication between any two entities will have to pass through all intermediate ones. In such a simpler topology, each host or device is identified simply by a Loop ID. Figure 4-4 Fibre Channel Private Loop
A private loop topology allows up to 126 nodes to be connected. The Loop ID of FC devices can be set through dial settings on the device itself. The Loop ID for host adapters is attained automatically through the fibre channel initialization process. A private loop topology can be formed by connecting adjacent nodes to each other directly or by interconnecting them through an FC Hub. The hub internally connects the receive and transmit wires of adjacent nodes to form the loop. The main advantage of using hub is that it electrically bypasses inactive ports, thus allowing loop communication to happen even if any of the nodes goes faulty. There is also another variant of the arbitrated loop topology called Public Loop which results when an FC switch is introduced as part of an arbitrated loop. But as far as fibre channel protocol is concerned, this is considered to be covered under the fabric topology itself. Another simpler topology is the Point-to-Point topology where a single device is connected to a single host by means of a direct connection. Some fibre channel protocol operations followed in a "point-to-point" topology is different from the private loop and fabric topologies. Figure 4-5 Fibre Channel Point-to-Point