[Fibre Channel] The “Fabric” port within a Fibre Channel fabric switch that provides a point-to-point link attachment to a single N_Port.

F_Ports are intermediate ports in virtual point-to-point links between end system ports, for example the N_Port on an end node to the F_Port on a switch to the F_Port in that switch to the N_Port on the other end node using a single Fibre Channel fabric switch. An F_Port is assumed to always refer to a port to which non-loop PN_Ports are attached to a Fabric, and does not include FL_Ports [FC-FS-2].

F_Port name

[Fibre Channel] A Name_Identifier associated with an F_Port.


[Fibre Channel] An entity consisting of one or more Switches that interconnect various Nx_Ports attached to it, and capable of routing frames using only the D_ID information in an FC-2 frame header.

Fabric_Identifier (F_ID)

[Fibre Channel] An identifier assigned to each Fabric in an Inter-Fabric Routing environment.


[Fibre Channel] A Name_Identifier associated with a fabric.

Fabric Login

[Fibre Channel] The process by which a Fibre Channel node establishes a logical connection to a fabric switch.

Fabric Provided MAC Address (FPMA)

[Fibre Channel] [Network] A MAC address that is assigned by an FCF and is fabric-wide unique.


[Computer System] The restoration of a failed system component’s share of a load to a replacement component after a failback event.

When a failed controller in a redundant configuration is replaced, the devices that were originally controlled by the failed controller are usually failed back to the replacement controller to restore the I/O balance, and to restore failure tolerance. Similarly, when a defective fan or power supply is replaced, its load, previously borne by a redundant component can be failed back to the replacement part.

failed over

[Computer System] A mode of operation for failure tolerant systems in which a component has failed and its function has been assumed by a redundant component.

A system that protects against single failures operating in failed over mode is not failure tolerant, since failure of the redundant component may render the system unable to function. Some systems (e.g., clusters) are able to tolerate more than one failure; these remain failure tolerant until no redundant component is available to protect against further failures.


[Computer System] The automatic substitution of a functionally equivalent system component for a failed one.

The term failover is most often applied to intelligent controllers connected to the same storage devices and host computers. If one of the controllers fails, failover occurs, and the survivor takes over its I/O load.

failure tolerance

[Computer System] The ability of a system to continue to perform its function (possibly at a reduced performance level) when one or more of its components has failed.

Failure tolerance in disk subsystems is often achieved by including redundant instances of components whose failure would make the system inoperable, coupled with facilities that allow the redundant components to assume the function of failed ones.


[File System] [Network] Acronym for File Area Network.


[Storage System] Synonym for device fanout.

fast mirror resynchronization

[Data Recovery] A technique for reducing the time required to synchronize a split mirror with the set of storage devices from which it was split.

Fast mirror resynchronization requires that a list of changes to the original set of data since moment of splitting be kept. When the split mirror is rejoined to the original set of volumes, only the data items identified in the list are copied from the original to the split mirror rather than the entire contents of the devices.

fast SCSI

[SCSI] A form of SCSI that provides 10 megatransfers per second.

Wide fast SCSI has a 16-bit data path, and transfers 20 MBytes per second. Narrow fast SCSI transfers 10 MBytes per second. See wide SCSI, Ultra SCSI, Ultra2 SCSI, Ultra3 SCSI.

fault tolerance

[Computer System] Synonym for failure tolerance.


[Storage System] Acronym for Fixed Block Architecture.


[Fibre Channel] Acronym for Fibre Channel.


[Fibre Channel] The Fibre Channel protocol level that encompasses the physical characteristics of the interface and data transmission media.


[Fibre Channel] The Fibre Channel protocol level that encompasses 8B/10B encoding, and transmission protocol


[Fibre Channel] The Fibre Channel protocol level that encompasses signaling protocol rules and the organization of data into frames, sequences, and exchanges.


[Fibre Channel] The Fibre Channel protocol sublevel, that routes frames between VN_Ports and LCFs, based on the D_ID in the Frame_Header and the VF_ID in the VFT_Header if there is a VFT_Header.


[Fibre Channel] The Fibre Channel protocol sublevel, that defines the rules and provides mechanisms that shall be used to transfer frames via the FC-1 level.


[Fibre Channel] The Fibre Channel protocol sublevel, that defines functions and facilities that a VN_Port may provide for use by an FC-4 level, regardless of the FC-1 that is used.


[Fibre Channel] The Fibre Channel protocol level that defines a set of services that are common across multiple Nx_Ports of a node.

FC-3 includes protocols for Basic Link Services, Extended Link Services and Hunt Groups.


[Fibre Channel] The Fibre Channel protocol level that encompasses the mapping of upper layer protocols (ULP) such as IP and SCSI to lower protocol layers (FC-0 through FC-3).

An example of an FC-4 standard is the mapping of SCSI commands to Fibre Channel (FCP-3).


[Fibre Channel] Shorthand for Fibre Channel Avionics Environment.



[Fibre Channel] Shorthand for Fibre Channel Arbitrated Loop.

In this and other FC-related entries, the numbers denote versions of the spec, developed and maintained by the INCITS T11 committee, that bears that name. The listed version is current as of this writing.


[Fibre Channel] Shorthand for Fibre Channel Audio Video.



[Fibre Channel] Shorthand for Fibre Channel Backbone.

When used, the number denotes a version of the spec. The listed version is current as of this writing.


[Fibre Channel] Shorthand for Fibre Channel Device Attach.



[Fibre Channel] Shorthand for Fibre Channel Framing and Signaling.

When used, the number denotes a version of the spec. The listed version is current as of this writing.



[Fibre Channel] Shorthand for Fibre Channel Generic Services.

When used, the number denotes a version of the spec. The listed version is current as of this writing.


[Fibre Channel] Shorthand for Fibre Channel Inter-Fabric Routing.



[Fibre Channel] Shorthand for Fibre Channel Link Services.

When used, the number denotes a version of the spec. The listed version is current as of this writing.


[Fibre Channel] Shorthand for Fibre Channel Methodologies for Interconnects.

When used, the number denotes a version of the spec. The listed version is current as of this writing.


[Fibre Channel] Shorthand for Fibre Channel NVMe.




[Fibre Channel] Shorthand for Fibre Channel Physical Interface.

When used, the number denotes a version of the spec. The listed versions are current as of this writing.


[Fibre Channel] A port that is capable of transmitting and receiving Fibre Channel frames according to the FC-0, FC-1, FC-2, and FC-3 levels of the Fibre Channel standards.

An FC_Port includes an LCF and at least one Nx_Port. The following are FC_Ports: PN_Ports, L_Ports, F_Ports, FL_Ports, Fx_Ports, E_Ports, and B_Ports.




[Fibre Channel] Shorthand for Fibre Channel Single Byte (command set).


[Fibre Channel] Shorthand for Fibre Channel Security Protocols.



[Fibre Channel] Shorthand for Fibre Channel Switched (fabric interconnect).

When used, the number denotes a version of the spec. The listed versions are current as of this writing.


[Fibre Channel] Shorthand for Fibre Channel Virtual Interface.

FC Entity

[Fibre Channel] [Network] The interface between an FC Switching Device or an FC stack and the FCoE Entity.

Each FC Entity contains a single instance of either a VE_Port, a VF_Port, or a VN_Port.


[Fibre Channel] Shorthand for Fibre Channel Association.


[Fibre Channel] Shorthand for Fibre Channel Data-Plane Forwarder


[Fibre Channel] Shorthand for FCoE Forwarder.


[Fibre Channel] Shorthand for Fibre Channel Industry Association.


[Fibre Channel] [Network] Acronym for Fibre Channel over Ethernet.

FCoE Controller

[Fibre Channel] [Network] A functional entity, coupled with a Lossless Ethernet MAC, that instantiates VE_Ports, VF_Ports, and VN_Ports, and/or creates FCoE_LEPs.

FCoE Entity

[Fibre Channel] [Network] The interface between the FC Entity and a Lossless Ethernet MAC. Each FCoE Entity contains one or more FCoE_LEPs.

FCoE Forwarder (FCF)

[Fibre Channel] [Network] A Fibre Channel Switching Device with one or more Lossless Ethernet MACs, each coupled with an FCoE Controller, and optionally one or more Lossless Ethernet bridging devices and optionally an FC Fabric interface.

An FCF forwards FCoE frames addressed to one of its FCF-MACs based on the D_ID of the encapsulated FC frames.

FCoE Initialization Protocol (FIP)

[Fibre Channel] [Network] A protocol that enables the discovery and instantiation, and maintenance of FCoE devices.

FCoE Link Endpoint (FCoE_LEP)

[Fibre Channel] [Network] The data forwarding component of an FCoE Entity that handles FC frame encapsulation/decapsulation, and transmission/reception of encapsulated frames through a single Virtual Link.

FCoE Node (ENode)

[Fibre Channel] [Network] A Fibre Channel Node with one or more Lossless Ethernet MACs, each coupled with an FCoE Controller.


[Fibre Channel] Shorthand for Fibre Channel Protocol.


[SCSI] A series of standards that describes the operation of the SCSI protocol over Fibre Channel links.


[Network] Acronym for Fiber Distributed Data Interface.

FDDI adapter

[Network] An adapter that connects an intelligent device to an FDDI network.

Both FDDI-fiber adapters that connect to optical fiber FDDI networks, and FDDI-TP adapters that connect to twisted copper pair FDDI networks exist. Although network interface cards are usually referred to as NICs rather than as adapters, the term FDDI adapter is more common than FDDI NIC. See NIC.

Federal Information Processing Standard (FIPS)

[Data Security] Standards (and guidelines) produced by NIST for government-wide use in the specification and procurement of Federal computer systems.

Federal Rules of Civil Procedure (FRCP)

[Legal] A set of regulations that specify procedures for civil legal suits within United States District (federal) Courts.

Federal district courts in all fifty states are required to follow these rules. Many state courts' civil procedural rules closely follow or adopt similarly worded rules.

See also FRCP

federated deduplication

[Storage System] Deduplication across multiple storage systems.

Federated Management Architecture Specification

[Management] [Network] A specification that defines a set of Java APIs for heterogeneous storage resource and storage network management.

This specification is a central technology of Jiro.

Fiber Distributed Data Interface (FDDI)

[Network] An ANSI standard for a token ring Metropolitan Area Networks (MANs), based on the use of optical fiber cable to transmit data at a rate of 100 Mbits/second.

Both optical fiber and twisted copper pair variations of the FDDI physical standard exist. FDDI is a completely separate set of standards from Fibre Channel. The two are not directly interoperable.


[Fibre Channel] The international spelling of the American word fiber.

The British spelling was selected for the Fibre Channel technology, though the American spelling is used to describe the fiber optic technologies defined for Fibre Channel.

Fibre Channel (FC)

[Fibre Channel] A serial I/O interconnect capable of supporting multiple protocols, including access to open system storage (FCP), access to mainframe storage (FICON), and networking (TCP/IP).

Fibre Channel supports point to point, arbitrated loop, and switched topologies with a variety of copper and optical links running at speeds from 1 Gb/s to 10 Gb/s. The committee standardizing Fibre Channel is the INCITS Fibre Channel (T11) Technical Committee.

Fibre Channel Arbitrated Loop (FC-AL)

[Fibre Channel] A form of Fibre Channel interconnect in which up to 126 nodes are connected in a loop topology, with each node's L_Port transmitter connecting to the L_Port receiver of the next node on the loop.

Nodes connected to a Fibre Channel Arbitrated Loop arbitrate for the single transmission that can occur on the loop at any instant using a Fibre Channel Arbitrated Loop protocol that is different from Fibre Channel switched and point to point protocols. An arbitrated loop may be private (no fabric connection) or public (attached to a fabric by an FL_Port). The network is defined by the FC-AL-2 standard INCITS 332 - 1999 [R2004].

Fibre Channel Avionics Environment (FCAE)

[Fibre Channel] The technical report describing a specific subset of Fibre Channel for use in defense and avionic applications.

Fibre Channel Backbone (FC-BB)

[Fibre Channel] A standard that defines mappings for transporting Fibre Channel over different network technologies, including operation of Fibre Channel over Ethernet (FCoE).

Fibre Channel Data-Plane Forwarder (FCDF)

[Fibre Channel] A simplified FC switching entity that forwards FC frames via A_Ports and F_Ports through an FCDF Switching Element.

Fibre Channel Device Attach (FC-DA)

[Fibre Channel] A technical report that selects and restricts logical options from the Fibre Channel Framing and Signaling, Fibre Channel Protocol for SCSI, Fibre Channel Arbitrated Loop, Fibre Channel Generic Services, and Fibre Channel Single Byte Command Set standards.

The intent of the technical report is to facilitate interoperability between devices whether they are connected in a loop or fabric topology.

Fibre Channel Framing and Signaling (FC-FS)

[Fibre Channel] A standard describing the framing and signaling requirements for Fibre Channel links.

Fibre Channel Generic Services (FC-GS)

[Fibre Channel] A standard describing in detail the Generic Services introduced in FC-FS-2, i.e., the name services, management services, and discovery services.

Fibre Channel Industry Association (FCIA)

[Fibre Channel] A mutual benefit corporation formed under the non-profit corporation laws of the State of California, whose members consist of companies that manufacture Fibre Channel systems, components, software, and tools, as well as provide Fibre Channel education and services to end-user customers.

Fibre Channel Interaction Space

[Fibre Channel] The set of Fibre Channel ports, devices, and Fabrics that are connected by Fibre Channel links or are accessible by a common instance of an administrative tool or tools.

Fibre Channel Inter-Fabric Routing (FC-IFR)

[Fibre Channel] A standard that specifies a set of protocols and methods to enable selective communication among Nx_Ports connected to different Fabrics.

Fibre Channel Link Services (FC-LS)

[Fibre Channel] A standard describing the Link Services for Fibre Channel links.

Fibre Channel Methodologies for Interconnects (FC-MI)

[Fibre Channel] A technical report specifying common methodologies for both arbitrated loop and switched environments, with the intention of facilitating interoperability between devices whether they are connected in a loop or Fabric topology.

Fibre Channel NVMe (FC-NVMe)

[Fibre Channel] The standard that describes the Fibre Channel mapping for communication between an NVMe host and an NVM subsystem.

Fibre Channel over Ethernet (FCoE)

[Fibre Channel] [Network] A technology that encapsulates Fibre Channel frames in Ethernet frames, allowing FC traffic to be transported over Ethernet networks.

Fibre Channel Physical Interface (FC-PI)

[Fibre Channel] The ANSI standard that describes the point-to-point physical interface of a high-performance serial link for support of the higher level protocols associated with HIPPI, IPI, SCSI and others.

Fibre Channel Protocol (FCP)

[Fibre Channel] The serial SCSI command protocol used on Fibre Channel interconnects.

FCP standardization is the responsibility of the INCITS TC-T10 committee.

Fibre Channel Security Protocols (FCSP)

[Fibre Channel] An ANSI standard that describes the protocols used to implement security in a Fibre Channel fabric.

This standard includes the definition of protocols to authenticate Fibre Channel entities, protocols to set up session keys, protocols to negotiate the parameters required to ensure frame-by-frame integrity and confidentiality, and protocols to establish and distribute policies across a Fibre Channel fabric.

Fibre Channel Service Protocol (FSP)

[Fibre Channel] A FC-4 protocol that defines all services independently of topology or fabric type.

Fibre Channel Single Byte (command set) (FC-SB)

[Fibre Channel] The industry standard command protocol for ESCON over Fibre Channel.

The second and third versions of this protocol are known as FC-SB-2 and FC-SB-3 respectively.

Fibre Channel Switched (fabric interconnect) (FC-SW)

[Fibre Channel] A standard that describes the requirements for an interconnecting fabric consisting of multiple fabric switch devices to support the ANSI/INCITS Fibre Channel protocols.

Fibre Channel Virtual Interface (FC-VI)

[Fibre Channel] A standard for application-level distributed interprocess communication based on Intel Corporation's V1.0 Virtual Interface (VI) Architecture; formerly known as VIA.

Fibre Connect (FICON)

[Fibre Channel] IBM Corporation's implementation of the Fibre Channel Single Byte Command Set standards., developed to provide a Fibre Channel compatible implementation of ESCON.


[Fibre Channel] Acronym for Fibre Connect.

Field Replaceable Unit (FRU)

[Computer System] A unit, or component of a system that is designed to be replaced “in the field;” i.e., without returning the system to a factory or repair depot.

Field replaceable units may either be customer-replaceable, or their replacement may require trained service personnel. See Customer Replaceable Unit.


[File System] An abstract data object made up of (a.) an ordered sequence of data bytes stored on a disk or tape, (b.) a symbolic name by which the object can be uniquely identified, and (c.) a set of properties, such as ownership and access permissions that allow the object to be managed by a file system or backup manager.

Unlike the permanent address spaces of storage media, files may be created and deleted, and in most file systems, may expand or contract in size during their lifetimes.

File Area Network (FAN)

[File System] [Network] A namespace-based network-oriented infrastructure for files that includes a decoupling layer that separates logical file access from physical file location, and enables a variety of services (e.g., replication and migration) to be applied to files and file systems.

file extent

[File System] A logically contiguous region of file data.

file level deduplication

[File System] Reduction of file copies by replacing duplicates with pointers to a single original file.

See data deduplication.

file mark

[Storage System] A data separator within a volume.

file server

[File System] A computer whose primary purpose is to serve files to clients.

A file server may be a general purpose computer that is capable of hosting additional applications or a special purpose computer capable only of serving files. See filer.

file system

[File System] A software component that imposes structure on the address space of one or more physical or virtual disks so that applications may deal more conveniently with abstract named data objects of variable size (files).

File systems are often supplied as operating system components, but are also implemented and marketed as independent software components.

Spelling filesystem as a single word is also correct, especially when the term is used as an adjective.

file system virtualization

1. [File System] The act of aggregating multiple file systems into one large virtual file system, so that users access data objects through the virtual file system and are unaware of the underlying partitioning.

2. [File System] The act of providing additional new or different functionality, e.g., a different file access protocol, on top of one or more existing file systems.

file virtualization

1. [File System] The use of virtualization to present several underlying file or directory objects as one single composite file.

2. [File System] The use of virtualization to provide HSM like properties in a storage system.

3. [File System] The use of virtualization to present an integrated file interface when file data and metadata are managed separately in the storage system. See block virtualization.


[File System] An intelligent network node whose hardware and software are designed to provide file services to client computers.

Filers are pre-programmed by their vendors to provide file services, and are not normally user programmable. See appliance, file server.

fill word [Out of Order. Fix it?]

[Fibre Channel] A transmission word that is an idle or an ARBx primitive signal.

Fill words are transmitted between frames, primitive signals, and primitive sequences to keep a fibre channel network active.


[Data Recovery] Acronym for Frozen Image Method.


[Storage System] An identifier derived from the data, used to detect redundancy.


[Data Security] Acronym for Federal Information Processing Standard.


[Computer System] Low-level software for booting and operating an intelligent device.

Firmware generally resides in read-only memory (ROM) on the device.

First Burst

[Fibre Channel] An optimization for the transmission, by an initiator, of the first DATA IU in a Data Series for a write operation.

Fixed Block Architecture (FBA)

[SCSI] A model of disks in which storage space is organized as linear, dense address spaces of blocks of a fixed size.

Fixed block architecture is the disk model on which SCSI is predicated. See count-key-data.

fixed content

1. [Data Management] Content that does not change.

2. [Data Management] Content that is prevented from change by the storage container in which it is kept.

fixed content storage

[Storage System] Storage systems and technology specialized for storing fixed content (i.e., data that does not change).

fixed-length segmentation

[Storage System] Partitioning a byte stream into parts that are a constant number of bytes when performing compression or hash-based data deduplication.

See variable-length segmentation.


[Fibre Channel] A “Fabric Loop” port within a Fibre Channel fabric switch, capable of Fibre Channel Arbitrated Loop operations and connected to one or more NL_Ports via a Fibre Channel Arbitrated Loop.

An FL_Port becomes a shared entry point for public NL_Port devices to a Fibre Channel fabric. FL_Ports are intermediate ports in virtual point-to-point links between end ports that do not reside on the same loop, for example the NL_Port on an end node to the FL_Port on a switch to the F_Port in that switch to the N_Port on that end node through a single Fibre Channel fabric switch.

flash array

[Storage System] Synonym for solid state storage array.

flash memory

[Hardware] A type of non-volatile memory used in solid state storage.

flash memory array

[Storage System] Synonym for solid state storage array.


[Fibre Channel] Short for Fabric LOGIn.

flywheel UPS

[Energy] A UPS that uses the momentum of a spinning disk or wheel to temporarily generate electricity in the event of a data center power failure.

Flywheel energy storage technology provides the bridge between normal power distribution and backup diesel generators and can replace conventional battery rooms.


[Data Recovery] Acronym for Fast Mirror Resynchronization.


[Solid State] Industry-speak for the new out-of-the-box state of an FRU, especially in reference to flash storage.

forensic copy

[Data Security] An accurate bit-for-bit reproduction of the information contained on an electronic device or associated media, whose validity and integrity has been verified using an accepted algorithm. [NIST SP 800-72]

formatted capacity

[Storage System] The total amount of bytes available to be written after a system or device has been formatted for use, e.g., by an object store, filesystem or block services manager.

Formatted capacity, also called usable capacity, is less than or equal to raw capacity. It does not include areas set aside for system use, spares, RAID parity areas, checksum space, host- or filesystem-level remapping, "right sizing" of disks, disk labeling and so on. However, it may include areas that are normally reserved—such as snapshot setasides—if they can alternatively be configured for ordinary data storage by the storage admin.


[Storage System] The preparation of a disk for use by writing required information on the media.

Disk controllers format disks by writing block header and trailer information for every block on the disk. Host software components such as volume managers and file systems format disks by writing the initial structural information required for the volume or file system to be populated with data and managed.

forward error correction (FEC)

[Data Recovery] A set of algorithms that perform corrections that allow for recovery of one or more bit errors.


[Fibre Channel] An ordered series of words that is the basic unit of data transmission in a Fibre Channel network.

A Fibre Channel frame consists of a Start of Frame Word (SoF) (40 bits); a Frame Header (8 Words or 320 bits); data (0 to 524 Words or 0 to 2192 ten bit encoded bytes; a CRC (One Word or 40 bits); and an End of Frame (EoF) (40 bits). See data frame.

frame content

[Fibre Channel] The information contained in a frame between its Start-of-Frame and End-of-Frame delimiters, excluding the delimiters.


[Fibre Channel] A sequence of words that follows the SOF delimiter and any Extended_Headers in a frame to control link operations and device protocol transfers as well as detect missing or out of order frames.

Frame Scrambling

[Fibre Channel] A technique for lowering the electromagnetic emission from Fibre Channel equipment by encoding frame content in a way to minimize repetitive bit sequences.

Frame Scrambling is required for operation at 8GFC.


[Legal] Acronym for Federal Rules of Civil Procedure.

free capacity

Deprecated synonym for free space.

free space

1. [Data Management] The amount of capacity reported to an end user as unused assigned capacity.

In a simple world, free space is normally the same as assigned capacity less the amount of assigned capacity already written. But restrictions such as quotas and interactions between systems using different arithmetic may cause the reported free space to vary from the actual quantity.

2. [Storage System] The amount of capacity reported to the storage admin as unused formatted capacity.

front domain

[Fibre Channel] A domain presented by a front domain switch.

front domain switch

[Fibre Channel] A switch within an Inter-Fabric Router that provides connectivity to the Fabrics that are interconnected by the Inter-Fabric Router.


[Computer System] Acronym for Field Replaceable Unit.

frozen image

[Data Recovery] Synonym for point in time copy.

Frozen Image Method (FIM)

[Data Recovery] A method by which a frozen image of a set of data can be generated.

Split mirrors and copy-on-write snapshots are the two common methods of generating frozen images.


[Fibre Channel] Acronym for Fibre Channel Service Protocol.

full backup

[Data Recovery] A backup in which all of a defined set of data objects are copied, regardless of whether they have been modified since the last backup.

A full backup is the basis from which incremental backups are taken. See cumulative incremental backup, differential incremental backup.

full duplex

[Data Communication] Concurrent transmission and reception of data on a single link.

full volume transfer rate

[Storage System] The average rate at which a single disk transfers a large amount of data (e.g., more than one cylinder) in response to one I/O request.

The full-volume data transfer rate accounts for any delays (e.g., due to inter-sector gaps, inter-track switching time and seeks between adjacent cylinders) that may occur during the course of a large data transfer. Full volume transfer rate may differ depending on whether data is being read or written. If this is true, it is appropriate to speak of full-volume read rate or full-volume write rate. Also known as spiral data transfer rate.


[Fibre Channel] A Switch Port capable of operating as an F_Port or FL_Port.