E_Port
[Fibre Channel] The “Expansion” port within a Fibre Channel switch that connects to another Fibre Channel switch or bridge device via an inter-switch link.
E_Ports are used to link Fibre Channel switches to form a multi-switch fabric.
EAL
[Data Security] Acronym for Evaluation Assurance Level.
EB
EByte
[General] Shorthand for Exabyte.
Ebit
[General] Shorthand for Exabit.
EBU
[Standards] Acronym for European Broadcast Union.
ECC
[Storage System] [Data Communication] Acronym for Error Correcting Code.
EcoStor™
[Standards] [Storage System] A family of SNIA standards for storage power management and related technologies.
EDE
[Data Security] Acronym for Encryption-Decryption-Encryption.
e-discovery
[Data Security] Short for electronic discovery.
EE_buffer
[Fibre Channel] A buffer associated with end-to-end flow control.
EE_credit
[Fibre Channel] A credit scheme used to manage end-to-end flow control during the exchange of frames between two communicating devices.
effective capacity
[Storage System] The amount of data stored on a storage system, plus the amount of unused formatted capacity in that system.
There is no way to precisely predict the effective capacity of an unloaded system. This measure is normally used on systems employing space optimization technologies.
An estimated calculation may be made as follows. Let D = the size of data already stored, Fd be the formatted capacity used to store that data, and Ft be the total formatted capacity on the system. Then the estimated effective capacity Ee is given by the formula
Ee = D / (Fd / Ft). No unused formatted capacity is used in the estimation calculation.
effective capacity power efficiency
[Storage System] The ratio of the effective capacity of an idle storage system to the amount of power required to maintain the system in a ready idle state.
egress routing function
[Fibre Channel] An entity within a Routing Function that performs the egress routing function role.
egress routing function role
[Fibre Channel] A process within a Routing Function that validates the frame, translates the S_ID, and then forwards the frame to the Native Fabric.
Eibit
[General] Shorthand for Exbibit.
EiB
EiByte
[General] Shorthand for Exbibyte.
electrical efficiency
[Computer System] The efficiency of any electrical device which transforms one type of power into another.
Efficiency is defined as output power divided by input power expressed as a percentage. All electrical components in a computer system, such as PDUs, UPSs and power supplies, incur some degree of power loss. Determining the total power loss in smaller systems with one power supply can be done by straightforward measurement of wall plug power and the total power supplied at the power supply's outputs. Larger systems require more complex methods.
electronic discovery
[Legal] The pretrial process of discovering pertinent stored information or data by one or both parties involved in a legal action or proceeding.
electronic storage element
[Storage System] Synonym for Solid State Disk.
Electronically Stored Information (ESI)
[Legal] Computer generated data or information of any kind and from any source, whose temporal existence is evidenced by its storage in, or on any electronic medium, wherever located, now existing or developed in the future, and irrespective whether such medium is real, virtual or otherwise. [ABA E-Discovery & Digital Evidence (EDDE) Committee]
The issue as to whether "unstable" or ephemeral information such as RAM is discoverable as ESI is a developing area and is fact-specific. Some court decisions have held that in certain cases RAM is discoverable ESI, and in certain others have ruled against discovery of such ESI. Clouding the issue further is the increasing trend by enterprises to use unstable data (e.g., RAM) as actual storage, and hard drive space as backup. [ABA E-Discovery & Digital Evidence (EDDE) Committee]
Note that the above definition and discussion paragraph have been provided by the American Bar Association (ABA), and are reproduced here as a courtesy to the ABA and the SNIA membership. The SNIA's position is that controversial legal terms are best defined by legal practitioners with a knowledge of recent case law.
embedded controller
embedded storage controller
[Storage System] An intelligent storage controller that mounts in a host computer’s housing and attaches directly to a host’s internal I/O bus.
Embedded controllers obviate the need for host bus adapters and external host I/O buses. Embedded storage controllers differ from host bus adapters in that they provide functions beyond I/O bus protocol conversion (e.g., RAID).
Enc_Header
[Fibre Channel] An encapsulation header used for forwarding FC frames from a source Routing Function to a destination Routing Function.
Encapsulating Security Payload (ESP)
[Data Security] A component of IPsec that permits the specification of various confidentiality mechanisms.
encoding
[Fibre Channel] Generation of transmission characters from valid data bytes and special codes.
encryption
[Data Security] The conversion of plaintext to encrypted text with the intent that it only be accessible to authorized users who have the appropriate decryption key.
End Of Frame (EOF)
[Fibre Channel] A group of ordered sets that delineates the end of a frame.
end-to-end encryption
[Data Security] Encryption of information at its origin and decryption at its intended destination without intermediate decryption.
end-to-end flow control
1. [Network] Control of message flow between the two end parties to a communication on a network.
2. [Fibre Channel] Flow control that occurs between two communicating Fibre Channel Nx-Ports.
end-to-end security
[Data Security] Safeguarding information in an information system from point of origin to point of destination. [CNSSI-4009]
energy efficiency
[Computer System] The power efficiency of a system over time.
While power and energy efficiency look about the same to a layman, the numbers may be different (even neglecting the units) on account of temporal variations in supply voltages, power and load factors and so on.
Enhanced Transmission Selection (ETS)
[Network] A DCB component that specifies a frame scheduling mechanism to support the allocation of bandwidth amongst traffic classes that share a link.
ENode MAC address
[Fibre Channel] [Network] The MAC address used by the ENode during the FCoE Initialization Protocol (FIP).
Enterprise Resource Management (ERM)
[Management] [Network] Software that manages all aspects of an organization's assets, systems, services and functions.
ERM systems manage a set of resources in the wider perspective of an organization's entire business. Managing in an enterprise context requires that entities be named uniquely and locatable within the enterprise, that heterogeneity of platforms and services may be assumed, and that the dynamic nature of the environment is taken into account.
Enterprise Systems Connection (ESCON)
[Storage System] A 200 Mbps serial I/O bus used on IBM Corporation’s Enterprise System 9000 data center computers.
Similar to Fibre Channel in many respects, ESCON is based on redundant switches to which computers and storage subsystems connect using serial optical connections.
entropy
[Data Security] A measure of the amount of uncertainty that an attacker faces to determine the value of a secret. [NIST SP 800-63]
The value is sometimes measured in bits of security strength, where a value of 0 indicates no security strength (i.e., full predictability or no randomness) and a positive value indicates increasing security strength.
entry port
[Data Recovery] A port—called both an entry port or an exit port—in a media library through which media can be inserted or removed without exposing internal library components.
EOF
1. [Fibre Channel] Acronym for End of Frame.
2. [File System] A designation or marker for the end of a file.
ERM
[Management] [Network] Acronym for Enterprise Resource Management.
Error Correcting Code (ECC)
[Storage System] [Data Communication] A scheme for checking the correctness of data that has been stored and retrieved, and correcting it if necessary.
An ECC consists of a number of bits computed as a function of the data to be protected, and appended to the data. When the data and ECC are read, the function is recomputed, the result is compared to the ECC appended to the data, and correction is performed if necessary. Error correcting codes differ from cyclic redundancy checks in that the latter can detect errors, but are not generally capable of correcting them. See cyclic redundancy check.
ESCON
[Storage System] Acronym for Enterprise Systems Connection.
ESI
[Legal] Acronym for Electronically Stored Information.
ESP
[Data Security] Acronym for Encapsulating Security Payload.
Ethernet
[Network] A local area networking technology based on packetized transmissions between physical ports over a variety of electrical and optical media.
Ethernet can transport any of several upper layer protocols, the most popular of which is TCP/IP. Ethernet standards are maintained by the IEEE 802.3 committee.
The unqualified term Ethernet usually refers to 10 Mbps transmission on multi-point copper. Fast Ethernet is used to denote 100 Mbps transmission, also on multipoint copper facilities. Ethernet and Fast Ethernet both use CSMA/CD physical signaling. Gigabit Ethernet (abbreviated GBE) transmits at 1250 Megabaud (1 Gbit of data per second) using 8b/10b encoding with constant transmission detection.
Ethernet adapter
[Network] An adapter that connects an intelligent device to an Ethernet network., usually called an Ethernet network interface card, or Ethernet NIC.
See NIC
European Broadcast Union (EBU)
[Standards] A European-based television (Video) standardization group coordinated with SMPTE and loosely affiliated with FC-AV.
Evaluation Assurance Level (EAL)
[Data Security] An assurance package or a reusable set of assurance components that are combined together to satisfy a set of identified security objectives.
The Common Criteria CC have provided seven predefined assurance packages, on a rising scale of assurance, that provide balanced groupings of the assurance components that are intended to be generally applicable.
evidence preservation
[Legal] A process to maintain and safeguard the integrity and/or original condition of the potential digital evidence. [ISO/IEC 1WD 27037]
EVSN
[Data Recovery] Acronym for External Volume Serial Number.
Exabit (Ebit)
[General] Shorthand for 1,000,000,000,000,000,000 (1018) bits.
The SNIA uses the base 10 convention commonly found in I/O-related and scientific literature rather than the base 2 convention (1,152,921,504,606,846,976, i.e., 260) common in computer system and software literature.
See also Exbibit.
Exabyte (EB)
[General] Shorthand for 1,000,000,000,000,000,000 (1018) bytes.
The SNIA uses the base 10 convention commonly found in I/O-related and scientific literature rather than the base 2 convention (1,152,921,504,606,846,976, i.e., 260) common in computer system and software literature.
See also Exbibyte.
Exbibit (Eibit)
[General] Shorthand for 1,152,921,504,606,846,976 (260) bits.
Binary notation is most commonly used for semiconductor memory sizes.
See also Exabit.
Exbibyte (EiB)
[General] Shorthand for 1,152,921,504,606,846,976 (260) bytes.
Binary notation is most commonly used for semiconductor memory sizes.
See also Exabyte.
exchange
[Fibre Channel] A set of one or more non-concurrent related sequences passing between a pair of Fibre Channel ports.
An exchange encapsulates a “conversation” such as a SCSI task or an IP exchange. Exchanges may be bidirectional and may be short or long lived. The parties to an exchange are identified by an Originator Exchange_Identifier (OX_ID) and a Responder Exchange_Identifier (RX_ID).
Exchange_Identifier
[Fibre Channel] A generic term denoting either an Originator Exchange Identifier (OX_ID) or a Responder Exchange Identifier (RX_ID).
exchange status block
[Fibre Channel] A data structure that contains the state of an exchange.
An originator N_Port or NL_Port has an Originator Exchange Status Block and a Responder N_Port or NL_Port has a Responder Exchange Status Block for each concurrently active exchange.
exclusive connection
[Fibre Channel] A Class 1 dedicated connection without intermix.
exit port
[Data Recovery] A port—also called an entry port—in a media library through which media can be inserted or removed without exposing internal library components.
expansion card
expansion module
[Computer System] A collective term for optional adapters in the form of printed circuit modules that can be added to intelligent devices.
Expansion cards include host bus adapters, network interface cards, as well as NVRAM, console, and other special purpose adapters.
expansion slot
[Computer System] A mounting and internal bus attachment device within an intelligent device into which expansion cards are inserted.
expired data
[Data Management] Data that is no longer required to be retained for any reason, becoming a candidate for permanent deletion.
Data may become expired when it has reached its defined retention period or when an event makes it obsolete and it has no further value to the organization. See disposition policy.
explicit addressing
[Storage System] A form of addressing used with disks in which the data’s address is explicitly specified in the access request.
See implicit addressing.
exploit
[Data Security] A defined way to breach the security of an IT system through a vulnerability.
export
1. [Computer System] Synonym for present, i.e., to cause to appear or make available.
2. [Computer System] To move objects, such as data, from within a system to a location outside the system, usually requiring a transformation during the move.
Disk array control software exports virtual disks to its host environment. In file systems, a directory may be exported or made available for access by remote clients.
Extended_Header
[Fibre Channel] A sequence of words that may be present in a frame between the SOF delimiter and the Frame_Header to support frame handling functions not enabled by the Frame_Header.
eXtensible Access Method (XAM)
[Standards] An interface standardized by the SNIA that provides applications with standard methods for storing data and associated metadata on fixed content storage.
The XAM Application Programming Interface (API) is being standardized by SNIA.
eXtensible Markup Language (XML)
[Standards] A universal format for structured documents and data on the World Wide Web.
The World Wide Web Consortium is responsible for the XML specification. See www.w3.org/XML.
extent
1. [Storage System] A set of consecutively addressed FBA disk blocks that is allocated to consecutive addresses of a single file.
2. [Storage System] A set of consecutively located tracks on a CKD disk that is allocated to a single file.
3. [Storage System] A set of consecutively addressed disk blocks that is part of a single virtual disk-to-member disk array mapping.
A single disk may be organized into multiple extents of different sizes, and may have multiple (possibly) non-adjacent extents that are part of the same virtual disk-to-member disk array mapping. This type of extent is sometimes called a logical disk.
external authentication
[Data Security] Deprecated synonym for third party authentication.
external controller
external disk controller
external storage controller
[Storage System] An intelligent storage controller that mounts outside its host computer’s enclosure and attaches to hosts via external I/O buses.
External storage controllers usually mount in the enclosure containing the disks they control.
External Volume Serial Number (EVSN)
[Data Recovery] A humanly readable volume serial number on a removable media or cartridge.
eye
[Data Communication] The center region of an eye diagram that does not occur for correctly formed signals, that distinguishes presence of signal (region above the eye) from absence of signal (region below the eye).
eye diagram
[Data Communication] A diagram used to specify optical or electrical signal transition characteristics for transmitters, in which the horizontal axis represents normalized time from pulse start and the vertical axis represents normalized amplitude.
eye opening
[Data Communication] Quantitative measure of the space in an eye diagram that does not occur for correctly formed signal transitions, and that prevents signal values from incorrectly being identified as high or low.
