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8B/10B Encoding

An encoding scheme, developed by IBM, that encodes 8-bit bytes into 10-bit transmission characters .


A Linear Tape- Open (LTO) tape format. Accelis tapes are dual-reel tapes with a capacity of up to 50 GB ( assuming 2:1 compression). Accelis tapes trade capacity for speed, in contrast to Ultrium tapes.


A printed circuit assembly that transmits data (I/Os) between the host system s internal bus and the external Fibre Channel link and vice versa. Also called an I/O adapter, host adapter, host bus adapter (HBA), or FC adapter.


The logical location of a peripheral device, node, or any other unit or component in a network. The formatted number specifying a network location.

See also [ SCSI Address ]

See also [ FC-AL Address ]


Arbitrated Loop Physical Address.

Arbitrated Loop

Fibre Channel Arbitrated Loop or FC-AL.

Arbitrated Loop Physical Address

The lower eight bits of the 24-bit native address identifier, the N_Port ID. 126 of the 256 possible values are used for addressing devices on a loop.


A process where devices on a Fibre Channel Arbitrated Loop contend for and gain temporary, exclusive access to loop resources.


The second byte of the N_Port Identifier.

Asynchronous Event Detection (HP s Event Monitoring Service)

The ability to detect an event at the time it occurs. When an event occurs, the monitor is immediately aware of it. This method provides quicker notification than polling.


Asynchronous Transfer Mode. A transport mechanism used in wide area networks.


The difference (loss) between transmitted and received power, due to the transmission loss through equipment lines or other communications devices. Fiber optic cable is expected to have minimum attenuation, although excessive bends or crimps in the medium can produce signal loss.

Auto Path XP

An optional software package for the XP256 disk array. It provides open (UNIX) and Windows NT systems with failover and load balancing capabilities over multiple paths from the server to the disk array.


The range of frequencies that can pass over a given circuit. Generally, the greater the bandwidth, the more information that can be sent through the circuit in a given amount of time. In data storage and data communications, bandwidth is usually expressed in terms of the amount of information sent over time, such as Mbps or Gbps.


The encoded bit rate per second. A measure of transmission speed.


A device used to connect a SCSI device to a Fibre Channel network. For example, the HP A3308A Fibre Channel/SCSI 4/2 Bridge can connect four SCSI devices to the SAN over two Fibre Channel paths.

Business Copy XP

An optional software package used with the XP256 disk array. It allows for rapid data copies between source and target volumes . Data copies are used in testing, development, data protection, and disaster recovery scenarios.

Cascaded FC_AL Hubs

One FC-AL hub connected to another FC-AL hub to increase distance or the number of ports in an arbitrated loop. Cascaded hubs allow distances up to 10 kilometers between hubs.

Class (of Service)

The types of services provided by the Fibre Channel topology and used by the communicating port. Class 1 is connection-oriented with acknowledged delivery. Class 2 is connectionless with acknowledged delivery. Class 3 (datagram service) is connectionless, with unacknowledged delivery. The device drivers determine if data is not received and needs to be retransmitted. Class 3 service is also known as send and pray service. Class 4 service is fractional service. It is connection-oriented and uses a fraction of the bandwidth of the link between two ports for communication between the ports. Class 6 service is known as unidirectional dedicated connection service. It is connection-oriented and provides (as the name indicates) dedicated unidirectional connections. Classes 4 and 6 are defined, but are not widely implemented.

Continuous Access XP

An optional software package used with the XP256 disk array. It allows for rapid data copies between source and target volumes, and is used for data protection and backups . Continuous Access copies may be made between volumes in the same disk array or between disk arrays that are remote from one another. It is frequently used in disaster recovery configurations.

Custom Volume Size

An optional software package used with the XP256 disk array. It permits the creation of LUNs smaller than the size of the physical disk, to improve performance and efficient use of space.


Digital Audio Tape. A family of small format (4 mm) helical scan tapes and tape drives , originally developed for recording audio. DDS tapes derive from the form factor, and are more widely used for recording data.


Digital Data System. A family of 4 mm helical scan tapes and tape drives, based on DAT technology. DDS tapes have evolved through several generations and are now at DDS-4. DAT tapes are less reliable and should not be used in DDS drives. Later DDS tapes use the Media Recognition System (MRS), indicated by metal markers on the tape, to tell a tape drive what generation of tape is being used. DDS-4 tapes hold 40 GB, assuming 2:1 compression. DDS tape is usually used to back up a single server or NAS device.

Default Monitoring Requests

The default monitoring configuration created when the EMS Hardware Monitors are installed. The default requests ensure that a complete level of protection is automatically provided for all supported hardware resources.


A property of 8B/10B encoded bytes. A byte has negative disparity if there are more binary ones in the byte than binary zeroes, and positive disparity if there are more zeroes than ones. A byte has neutral disparity when the number of binary ones equals the number of binary zeroes.


Digital Linear Tape. A tape technology widely used in backups. Current versions of DLT have a capacity of up to 80 GB, assuming 2:1 compression. DLT tapes are used in single mechanisms and in tape libraries storing from 10 to 1000 DLT cartridges.


The most significant byte in the N_Port Identifier for an FC device. It is not used in the FC-SCSI hardware path ID. It is required to be the same for all SCSI targets logically connected to an FC adapter.


A Fibre Channel switch expansion port, used to link Fibre Channel switches.


Event Monitoring Service.


Enterprise Systems Connection Architecture, an IBM technology used primarily for connecting mainframes to storage devices over fiber optic cable.

Event Monitoring Service

The application framework used for monitoring system resources on servers running HP-UX 10.20 and 11.0. Hardware monitoring uses the EMS framework for reporting events and creating PSM monitoring requests. A collection of EMS system monitors are available at additional cost and are not included with the hardware monitoring software.

Event Severity Level

An Event Monitoring Service term . Each event that occurs within the hardware is assigned a severity level, which reflects the impact the event may have on system operation. The severity levels provide the mechanism for directing event notification. For example, you may choose a notification method for critical events that will alert you immediately to their occurrence, and direct less important events to a log file for examination at your convenience. Also, when used with MC/ ServiceGuard to determine failover criteria, severe and critical events cause failover.


An F_Port on a Fibre Channel switch connects to an N_Port on a device.


An FL_Port on a Fibre Channel switch connects to an arbitrated loop.


A crosspoint switched network, which is one of three Fibre Channel topologies. A fabric consists of one or more fabric elements, which are switches responsible for frame routing. The fabric structure is transparent to the devices connected to it and relieves them of the responsibility for station management.

Fabric Switch

A device that enables the Fibre Channel fabric topology. A core building block of the Storage Area Network.


Fibre Channel Arbitrated Loop.

FC-AL Address

The eight-bit device address on a private Fibre Channel Arbitrated Loop. Addresses are assigned automatically on initialization.

FC-AL Device

A device that can be used in a Fibre Channel Arbitrated Loop. It has one or more NL_Ports.

FC-AL Port

The port on an FC-AL hub that provides connection between the FC-AL adapter and the FC-AL link. Hewlett-Packard FC-AL hubs are 10-port hubs.

FC-SCSI Hardware Path

A list of values, presented by the HP-UX ioscan command, showing the physical hardware path of the host to a target device. The format is:



Fiber optic cable.

Fiber Optic Cable

A cable made from thin strands of dielectric material, such as glass, through which data in the form of light pulses is transmitted by laser or LED. Fiber optic cable is used for high-speed transmission over medium to long distances.

Fiber Optics

A technology that uses light as an information carrier. Fiber optic cables are a direct replacement for conventional coaxial cable and wire pairs. The glass-based transmission medium occupies less physical volume for an equivalent transmission capacity, and the fibers are immune to electrical interference.


A generic Fibre Channel term used to describe all transmission media specified in the Fibre Channel Physical Layer standard (FC-PH), including optical fiber, copper twisted pair, and copper coaxial cable.

Fibre Channel

Logically, Fibre Channel is a bidirectional, full-duplex , point-to-point, serial data channel structured for high performance capability. Physically, Fibre Channel interconnects devices, such as host systems and servers, FC hubs and disk arrays, through ports, called N_Ports, in one of three topologies: a point-to-point link, an arbitrated loop, or a crosspoint switched network (also called a fabric). Fibre Channel can interconnect two devices in a point-to-point topology, from two to 126 devices in an arbitrated loop, and over 14 million devices in a fabric.

Fibre Channel is a generalized transport mechanism. It has no protocol or native I/O command set, but can transport any existing protocol, such as SCSI, in frames . Fibre Channel is capable of operating at speeds of 100 MBps (full speed), 50 MBps (half speed), 25 MBps (quarter speed), or 12.5 MBps ( eighth speed), over distances of up to 100 m over copper media or up to 10 km over fiber optic cable.

Fibre Channel Arbitrated Loop (FC-AL)

One of three Fibre Channel topologies, in which two to 126 ports can be interconnected serially in a single loop circuit. Access to the FC-AL is controlled by an arbitration scheme. The FC-AL topology supports all classes of service and guarantees in-order delivery of frames.

Fibre Channel Arbitrated Loop Hub

A full-duplex, 1 Gbps intelligent interconnection device, used in an FC-AL topology to create a loop. A maximum of ten devices can be connected to each FC-AL hub.

Fibre Channel Protocol for SCSI (FCP)

A high-level Fibre Channel mapping layer (FC-4) that uses lower-level Fibre Channel services (FC-PH) to transmit SCSI command, data, and status information between a SCSI initiator and a SCSI target across the Fibre Channel link using Fibre Channel frame and sequence formats.


A collection of bits that contain both control information and data; the basic unit of transmission on a network. Control information is carried in the frame with the data to provide for functions such as addressing, sequencing, flow control, and error control to the respective protocol levels. It can be of fixed or variable length.

The smallest, indivisible unit of data transfer used by Fibre Channel. Frame size depends on the hardware implementation and is independent of the application software. Frames begin with a 4-byte Start of Frame (SOF), end with a 4-byte End of Frame (EOF), include a 24-byte frame header and a 4-byte Cyclic Redundancy Check (CRC), and can carry a variable data payload from 0 to 2112 bytes, the first 64 of which can be used for optional headers.


A Fibre Channel switch port that can function either as an E_Port or as an F_Port.


Gigabit Interface Converter.


Gigabytes per second.


Gigabits per second.

Gigabit Interface Converter

A removable component of Fibre Channel host bus adapters that manages the functions of the FC-0 layer, which are the physical characteristics of the media and interface. HBAs have either a GBIC or a GLM.

Gigabit Link Module

A physical component that manages the functions of the FC-0 layer, which are the physical characteristics of the media and interface, including driver, transceivers, connectors, and cables. Also referred to as a Physical Link Module (PLM).


Gigabit Link Module.


High Availability.

Hardware Event Monitor

An Event Monitoring Service monitor daemon that gathers information about the operational status of hardware resources. Each monitor is responsible for watching a specific group or type of hardware resources. For example, the tape monitor handles all tape devices on the system. The monitor may use polling or asynchronous event detection for tracking events. Unlike a status monitor, an event monitor does not remember the occurrence of an event. It simply detects and reports the event. An event can be converted into a more permanent status condition using the Peripheral Status Monitor.

Hardware Event

An Event Monitoring Service term for any unusual or notable activity experienced by a hardware resource (for example, a disk drive that is not responding, or a tape drive that does not have a tape loaded). When any such activity occurs, the occurrence is reported as an event to the event monitor.

Hardware Resource

An Event Monitoring Service term for a hardware device used in system operation. Resources supported by hardware monitoring include mass storage devices such as disks and tapes, connectivity devices such as hubs and multiplexers, and device adapters.


Host Bus Adapter.

High Availability

A term applied to some disk arrays and clustered server configurations. High availability implies that the device can sense, report, and recover from some hardware failures. High availability components include redundant power supplies , fans, system processors (SPs), and RAID-enabled disk drives.


High Performance Parallel Interface. A high-speed interface.


A processor using a disk array for data storage and retrieval.

Host Bus Adapter (HBA)

A printed circuit assembly which transmits data between the host system s internal bus and the external Fibre Channel link and vice versa.


A device used to connect several nodes in a network. A hub is a concentration point for data and repeats data from one node to all other connected nodes.


In SCSI, the server that initiates an exchange with a disk or tape. The Fibre Channel equivalent term is originator.


An HP-UX command used to identify devices on a bus and determine their states.


Information Technology. An all-encompassing term for the information processing profession and work done with computers and data. The current name for the department formerly known as the MIS (Management Information Systems) Department, and before that, the Data Processing Department. Also the term for a course of study in colleges and universities.


Just a Bunch of Disks. A collection of disk drives in an enclosure, which may or may not have high availability characteristics.


Local Area Network.

Light Emitting Diode (LED)

A small light on a device that is often used to provide status information. LNK, LINK, ERR, STATUS, ACT, and POWER are typical LED labels.


In Fibre Channel, two unidirectional fiber cables, transmitting in opposite directions, and their associated transmitters and receivers. The link is the connection between nodes in a topology. Comparable to a bus in SCSI.


Loop Initialization Primitive. The sequence that allows for discovery of ports on the loop.

Logical Unit Size Expansion

An optional software package used with the XP256 disk array. It permits the creation of expanded LUNs, larger than the size of the physical disk.


Lasers or LEDs that emit light with wavelengths around 1300 nm. Longwave lasers are used for long Fibre Channel links, from approximately 700 to 10,000 meters . They are typically used with single-mode 9 micron fiber optic cable.

Longwave Hub

A Fibre Channel Arbitrated Loop hub employing long wave lasers and 9 micron single mode fiber optic cable.

Loop Address

The unique ID of a node in Fibre Channel loop topology, sometimes referred to as a Loop ID.

Loop Port (L_Port)

An N_Port or F_Port that supports arbitrated loop functions associated with arbitrated loop topology.


Linear Tape-Open. A new tape technology, specifying improved capacity and transfer rates over existing DDS and DLT technologies.


Logical Unit Number, or logical unit. A physical disk drive (or portion of it) that can be addressed as an entity. An HP-UX hardware path might show 8/, where the final zero represents LUN 0. For practical purposes, a drive (such as G:\ or I:\) on a Windows NT system. The XP256 disk array may have LUNs smaller than a disk, using the Custom Volume Size feature, or LUNs spanning disks, using the Logical Unit Size Expansion feature.


Megabits per second.


Megabytes per second.


Hewlett-Packard s application for creating and managing high availability clusters of HP 9000 Series 800 computers. A high availability computer system allows application services to continue in spite of a hardware or software failure. Hardware monitoring integrates with MC/ServiceGuard to detect and report hardware problems, allowing MC/ServiceGuard to take action to maintain system availability.

Monitoring Request

Event Monitoring Service settings that define how events for a specific monitor are handled by EMS. A monitoring request identifies the severity levels of interest and the type of notification method to use when an event occurs. A monitoring request is applied to each hardware device (or instance) supported by the monitor. Monitoring requests are created for hardware events using the Hardware Monitoring Request Manager. You create monitoring requests for changes in hardware status using the EMS GUI.


Node port. A hardware entity that performs data communication over the Fibre Channel link. It is identifiable by a unique World Wide Name (WWN). It can act as an originator or a responder .

N_Port Identifier

A unique 24-bit address by which an N_Port is known. The address consists of a Domain (most significant byte), an Area, and a Port, each 1 byte long. The N_Port identifier is used in the Source Identifier (S_ID) and Destination Identifier (D_ID) fields of a Fibre Channel frame.


Network Attached Storage.


A low-intensity laser transceiver whose output does not require OFC to turn off the laser when there is a disconnect.


The hardware device that allows for the transmission of data within a network. A node contains one or more ports.


Open Fibre Control. A safety feature used to prohibit laser light from functioning when there is a break or disconnect in a fiber cable. This is used with high-intensity lasers.


A wide area network leased line service connection, running at a speed of up to 155 Mbps.


A wide area network leased line service connection, running at a speed of up to 622 Mbps.


Online Transaction Processing.


The Fibre Channel N_Port responsible for starting an exchange. Fibre Channel term for a SCSI initiator.

Ordered Set

A transmission word beginning with a K28.5 special character. Ordered sets permit special control functions to be embedded in the bit stream, including frame delimiter , primitive signals, and primitive sequences.

Performance Manager XP

An optional software package used with the XP256 disk array. Its purpose is to monitor disk array performance, display real time status, capture the information in logs, and display a variety of performance graphs. The user may also make adjustments to settings on a real time or scheduled basis.

Peripheral Status Monitor (PSM)

Part of the Event Monitoring Service, the PSM is included with the hardware event monitors. It is a monitor daemon that acts as a hardware status monitor by converting events to changes in hardware resource status. This provides compatibility with MC/ ServiceGuard, which uses changes in status to manage cluster resources. The PSM is also used to create hardware status monitoring requests through the EMS GUI.


One of three Fibre Channel topologies. With the point-to-point topology, two devices are directly connected by a link with no fabric, loop, or switching elements present.


In event monitoring, the process of connecting to a hardware resource at regular intervals to determine its status. Any events that occur between polling intervals will not be detected until the next poll. If the event monitor supports asynchronous event monitoring, events will be reported immediately.


The hardware entity that connects a device to a Fibre Channel topology. A device can contain one or more ports.

Primitive Sequence

A set of three identical ordered sets for link control. These are used for notification of link failures and loss of synchronization.

Primitive Signal

Used for buffer-to-buffer flow control, or for idle primitives. Idles are words that fill the space between frames. In Fibre Channel, the transmitter must continuously send something over the media. This helps preserve bit, byte, and word synchronization, and permits faster communication.

Private Loop

A private loop is enclosed and known only to itself. A common example configuration uses FC-AL for Fibre Channel Mass Storage, and the processor node only has one Fibre Channel host bus adapter (HBA).


A formal set of rules governing the format, timing, sequencing, and error control of exchanged messages on a data network. It may also include facilities for managing a communications link and/or contention resolution. A protocol may be oriented toward data transfer over an interface, between two logical units directly connected, or on an end-to-end basis between two end users over a large and complex network. Both hardware protocols and software protocols can be defined.

Public Loop

A public loop extends the reach of the loop topology by attaching the loop to a fabric. Public loops are a way to leverage the cost of one switched connection over many devices in a loop.


Redundant Array of Independent Disks. A method of configuring multiple disk modules into a logical disk unit, which appears to the host system as a single, contiguous disk module.


A disk configuration with three or more disk modules bound as striped disks. The disk array reads and writes file information to more than one disk at a time. RAID-0 offers enhanced performance by using simultaneous I/O to different modules, but does not intrinsically offer high availability. For high availability, the striped disks can be software mirrored.


A disk configuration with even numbers of mirrored disk modules.


A disk configuration in which four, six, eight, ten, twelve, fourteen, or sixteen disk modules are bound as a mirrored RAID-0 group. The disk modules are mirrored such that one half the disk modules contain user data and the other half contain a disk-by-disk copy of the user data. A RAID-1/0 group combines the speed advantage of RAID-0 with the redundancy advantage of mirroring.


A disk configuration consisting of exactly five disk modules, each on a separate internal single-ended SCSI-2 bus. RAID-3 uses disk striping and a dedicated parity disk, but not hardware mirroring.


A disk configuration in which from three to sixteen disk modules use disk striping, with high availability provided by parity information distributed on each disk module. The ideal number of disk modules in a RAID-5 group is five.


Random Array of Independent Libraries.

Resource Instance

An Event Monitoring Service term for a specific hardware device. The resource instance is the last element of the resource path and is typically the hardware path to the resource (for example, 10_12_5.0.0), but it may also be a product ID as in the case of AutoRAID disk arrays. There may be multiple resource instances for a monitor, each one representing a unique hardware device for which the monitor is responsible.

Resource Path (EMS)

Hardware event monitors are organized into classes (and subclasses) for creating monitoring requests. These classes identify a unique path to each hardware resource supported by the monitor. Two similar resource paths exist for each hardware resource: an event path used for creating event monitoring requests, and a status path used for creating PSM monitoring requests.


The logical function in an N_Port responsible for supporting the exchange initiated by the originator in another N_Port. A Fibre Channel term for a SCSI target.


Storage Area Network.


Ultra3 SCSI. A type of SCSI using a 16 data-bit wide bus, and which transfers data at a maximum of 160 MB per second. Hewlett-Packard has chosen to support the SCSI-3 protocol over Fibre Channel for its mass storage environment.


Small Computer System Interface. An industry standard for connecting peripheral devices to a processor.

SCSI Address

A fast/wide SCSI adapter supports up to 16 devices, including itself. Each device has a unique SCSI address. The SCSI address of a device dictates the devices s priority when arbitrating for the SCSI bus. SCSI address 7 has the highest priority. The next highest priority address is 6 followed by 5, 4, 3, 2, 1, 0, 15, 14, 13, 12, 11, 10, 9, and 8. The SCSI adapter is factory set to address 7.

A narrow SCSI adapter supports up to eight devices, including itself. SCSI address 7 has the highest priority followed by 6, 5, 4, 3, 2, 1, and 0.


The conduit for transferring SCSI data between servers and SCSI devices through SCSI host bus adapters and SCSI ports.


An opening at the back of a SCSI device providing connection between the SCSI adapter and the SCSI bus. SCSI connectors come in 50-pin or 68-pin configurations.


Lasers or LEDs that emit light with wavelengths of 780 nm or 850 nm. Shortwave lasers are used for Fibre Channel links up to approximately 500 meters long, over multimode fiber. The preferred fiber core size is 50 microns. A 62.5 micron core size is also supported for compatibility with existing FDDI installations.

Shortwave Hub

A Fibre Channel Arbitrated Loop hub employing shortwave lasers and 50 or 62.5 micron multimode fiber optic cable.

Source Volume

The volume or LUN containing data to be copied to a target volume in Continuous Access or Business Copy operations on an XP256 disk array.


Simple Network Management Protocol.


Storage Processor.

Storage Area Network

An arrangement of storage devices, connected in a loop or fabric, using Fibre Channel.

Storage Processor

A printed-circuit board with memory modules that controls the disk modules in the storage system chassis. The SP runs Grid Manager, which is used to bind and unbind logical disk units, set up disk array caching, observe array status, and view the SP event log. The SP in a disk array divides the multiplexed SCSI-2 bus traffic from the host into five internal, single-ended, SCSI-2 buses (identified by the letters A, B, C, D, and E). Each internal SCSI-2 bus supports multiple logical units (LUNs).

Storage Node Manager

A SAN management software application made by Hewlett-Packard.


Short for data striping. (1) Used to achieve higher bandwidth, by allowing multiple links simultaneously and transmitting a single information unit across multiple links employing multiple N_Ports in parallel. Sometimes called port aggregation. (2) A mapping technique in which fixed-size consecutive ranges of virtual disk data addresses are mapped to successive array members in a cyclic pattern. RAID Level 0 or RAID 0.


For the purposes of SANs, a fabric switch. A Fibre Channel connection device that provides multiple, simultaneous full-bandwidth connections between devices.

T- 1

A wide area network leased line service connection, running at a speed of up to 1.544 Mbps.

T- 3

A wide area network leased line service connection, running at a speed of up to 45 Mbps.

Tape Library

A device containing one or more tape drives and a varying number of tapes. Tapes are moved from library slots to the drives under robot control. A small tape library might have one drive and ten slots for tapes. The largest HP tape library has 20 drives and 700 slots for tapes. Tape libraries are an essential component of backup and restore operations in large SANs.


In SCSI, the disk or tape device responding to an initiator. The Fibre Channel equivalent term is responder.

Target ID (TID)

The SCSI bus address of a controller or target device.

Target Volume

The volume or LUN receiving data from a source volume, using Continuous Access or Business Copy on an XP256 disk array.


The physical arrangement of devices on a network.


A Linear Tape-Open (LTO) tape format. First-generation Ultrium tapes currently have a capacity of up to 200 GB with 400 GB, 600 GB, and 1.6 TB on the generational roadmap (assuming 2:1 compression).


Wide Area Network.

World Wide Name

A 64-bit identifier assigned to a device. It uniquely identifies the device.


Limiting access by servers to LUNs, based on a device s World Wide Name. Implemented by HP s Secure LUN software.

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Storage Area Networks. Designing and Implementing a Mass Storage System
Storage Area Networks: Designing and Implementing a Mass Storage System
ISBN: 0130279595
EAN: 2147483647
Year: 2000
Pages: 88 © 2008-2017.
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