T1 copy

[Storage System] Synonym for mirroring.


[SCSI] Short name for the ANSI INCITS T10 technical committee.


[Fibre Channel] Short name for the ANSI INCITS TC T11 committee.

table routing method

[SCSI] A method used by SAS expanders for routing connection requests when multiple devices are accessible through a single SAS switch port.

tabular mapping

[Storage System] A form of mapping in which a lookup table contains the correspondence between the two address spaces being mapped to each other.

If a mapping between two address spaces is tabular, there is no mathematical formula that will convert addresses in one space to addresses in the other. See algorithmic mapping, dynamic mapping.


[Data Security] An unauthorized modification that alters the proper functioning of a device, system or communications path in a manner that degrades the security or functionality it provides.


[Storage System] A removable storage element containing a tape substrate used as a storage medium.

A tape cartridge may also contain other storage elements (e.g., a medium auxiliary memory). The data on a tape is accessed by a tape drive.

tape autoloader

[Storage System] Deprecated synonym for media stacker.

The term autoloader is typically used to indicate a low-cost library.

tape drive

[Storage System] A storage device that reads and writes data on tapes.

Unlike disks, tapes use implicit data addressing. See disk.

tape eject slot

[Storage System] An entry/exit slot in a tape library.

tape library

[Storage System] A storage device that provides automated access to multiple tape cartridges, typically via multiple tape drives.

A robotic media handler is used to move tape cartridges between the tape drives, tape slots (for storage), and tape eject slots if there are any.

tape slot

[Storage System] A physical location used to hold a tape cartridge when not in a tape drive.

tape virtualization
tape drive virtualization
tape library virtualization

[Storage System] The act of creating abstracted tape devices by applying virtualization to tape drives, tape libraries or other storage devices.


[SCSI] The endpoint that receives a SCSI I/O command sequence.

See initiator, LUN, target port identifier.

Target of Evaluation (TOE)

[Data Security] An IT product or system and its associated guidance documentation that is the subject of evaluation.

This term is most commonly associated with ISO 15408.

target port identifier

[SCSI] The interconnect address of a target or controller.

Target Session Identifying Handle (TSIH)

[iSCSI] An identifier, assigned by the iSCSI target, for a session with a specific named initiator.


[Computer System] Shorthand for Terabyte.


[General] Shorthand for Terabit.


[Data Security] Acronym for Trusted Computing Group.


[General] Acronym for Total Cost of Ownership.


[Network] Acronym for Transmission Control Protocol.

TCP Offload Engine (TOE)

[Network] A technology for improving TCP/IP performance by offloading TCP/IP processing to a Network Interface Card.


[Network] Shorthand for the suite of protocols that includes TCP, IP, UDP, and ICMP.

This is the basic set of communication protocols used on the Internet.

Tebibit (Tibit)

[General] Shorthand for 1,099,511,627,776 (240) bits.

Binary notation is most commonly used for semiconductor memory sizes.

See also Terabit.

Tebibyte (TiB)

[General] Shorthand for 1,099,511,627,776 (240) bytes.

Binary notation is most commonly used for semiconductor memory sizes.

See also Terabyte.

technical controls

[Data Security] Security controls (i.e., safeguards or countermeasures) for an information system that are primarily implemented and executed by the information system through mechanisms contained in the hardware, software, or firmware components of the system. [NIST Special Pub 800-53]

Technical Working Group (TWG)

[Standards] A SNIA working group in which specific technical work is undertaken, protected by the SNIA IP Policy.

Within the SNIA, technical work for standards development is conducted by volunteer technologists from member companies. The TWGs report to the SNIA Technical Council, which in turn reports to the SNIA Board.


[Fibre Channel] The possession of a Fibre Channel Arbitrated Loop by a device to conduct a transaction.

Terabit (Tbit)

[General] Shorthand for 1,000,000,000,000 (1012) bits.

The SNIA uses the base 10 convention commonly found in I/O-related and scientific literature rather than the base 2 convention (1,099,511,627,776, i.e., 240) common in computer system and software literature.

See also Tebibit.

Terabyte (TB)

[Computer System] Shorthand for 1,000,000,000,000 (1012) bytes.

The SNIA uses the base 10 convention commonly found in I/O-related and scientific literature rather than the base 2 convention (1,099,5111,627,776, i.e., 240) common in computer system and software literature.

See also Tebibyte.

test system

[Storage System] A collection of equipment used to perform a test.

In functional and performance testing, it is generally important to clearly define the test system, and distinguish it from the system under test.

theoretical capacity

[Storage System] The area of the storage media on a device times its areal density.

This number is rarely published, as it does little to contribute to an understanding of the eventual raw capacity of the device.

thin provisioning

[Storage System] A technology that allocates the physical capacity of a volume or file system as applications write data, rather than preallocating all the physical capacity at the time of provisioning.

third party authentication

[Data Security] Reliance on an authentication service, such as a RADIUS server, that is separate from (or external to) the entities of an authentication transaction.

third party copy

[Data Recovery] [Management] [SCSI] A technique for performing backups using minimal host resources by copying data directly from the source to the destination without passing through a host.


[Data Security] An avenue of attack that may result in adverse changes to a protected asset.

threat monitoring

[Data Security] Analysis, assessment, and review of audit trails and other information collected for the purpose of searching out system events that may constitute violations of system security.


[Computer System] The number of I/O requests satisfied per unit time.

Expressed in I/O requests/second, where a request is an application request to a storage subsystem to perform a read or write operation.


[General] Shorthand for Tebibyte.


[General] Shorthand for Tebibit.

tiered storage

[Storage System] Storage that is physically partitioned into multiple distinct classes based on price, performance or other attributes.

Data may be dynamically moved among classes in a tiered storage implementation based on access activity or other considerations.

time server

[Network] An intelligent entity in a network that enables all nodes in the network to maintain a common time base within close tolerances.


[Data Security] Acronym for Transport Layer Security.

TLS Handshake Protocol

[Data Security] A protocol that allows peers (the server and client) to agree upon security parameters for the record layer (TLS Record Protocol), authenticate themselves (key exchange), instantiate negotiated security parameters, and report error conditions to each other before the application protocol (such as HTTP, SMTP, etc.) transmits or receives its first byte of data.

The security parameters are actually created from the session identifier, certificates (X509v3), compression method, cipher spec (bulk encryption algorithm and a MAC algorithm), master secret, and resumability flag. The TLS Handshake Protocol is defined in RFC 2246.

TLS Record Protocol

[Data Security] A layered protocol that is used for encapsulation of various higher level protocols (such as HTTP, SMTP, etc.).

Using the security parameters created by the TLS Handshake Protocol, it takes messages to be transmitted, fragments the data into manageable blocks, optionally compresses the data, applies a MAC (such as MD5 or SHA), encrypts (such as NULL, DES, 3DES, etc.), and transmits the result. Received data is decrypted, verified, decompressed, and reassembled, then delivered to higher level clients. The TLS Record Protocol is defined in RFC 2246.


[Network] Acronym for Threaded Neil Councilman, a type of coaxial cable connector.

Specifications for TNC style connectors are defined in MIL-C-39012 and MIL-C-23329.


1. [Network] Acronym for TCP Offload Engine.

2. [Data Security] Acronym for Target of Evaluation.

token ring (network)

1. [Network] A network in which each node's transmitter is connected to the receiver of the node to its logical right, forming a continuous ring.

Nodes on a token ring network gain the right to transmit data by retaining a token (a specific unique message) when they receive it. When a node holding the token has transmitted its allotment of data, it forwards the token to the next node in the ring.

2. [Network] A LAN protocol for token ring networks governed by IEEE Standard 802.3 that operates at speeds of 4 Mbits/second and 16 Mbits/second.


1. [Network] The logical layout of the components of a computer system or network and their interconnections.

Topology deals with questions of what components are directly connected to other components from the standpoint of being able to communicate. It does not deal with questions of physical location of components or interconnecting cables.

2. [Fibre Channel] The communication infrastructure that provides Fibre Channel communication among a set of PN_Ports (e.g., a Fabric, an Arbitrated Loop, or a combination of the two).

Total Cost of Ownership (TCO)

[General] The comprehensive cost over its lifetime of a particular capability such as data processing, storage access, file services, etc.

TCO includes acquisition, environment, operations, management, service, upgrade, loss of service, and residual value. See inherent cost.


[Data Recovery] [Management] Acronym for Third Party Copy.


[Fibre Channel] A transmitter and receiver combined in one package.


[Long Term Retention] A type of migration in which a format or representation change occurs during the movement of data or information.

Transformation involves possible information loss, since newer formats may be incapable of capturing all the functionality of the original format, or the migration system may be unable to interpret all the nuances of the original format.

Translate Domain

[Fibre Channel] A domain presented by a Translate Domain switch.

Translate Domain switch

[Fibre Channel] A switch within an Inter-Fabric Router that is created for each set of Proxy N_Ports whose corresponding Native Nx_Ports exist within a set of Native Fabrics.

transmission character

[Fibre Channel] Any encoded character (valid or invalid) transmitted across the physical interface of a Fibre Channel or Ethernet link.

Valid transmission characters are specified by the standard defining the transmission code and include data characters and special characters.

transmission code

1. [General] A means of encoding data to enhance its transmission characteristics.

2. [Fibre Channel] A byte-oriented transmission code specified by FC-FS-2 for 1/2/4/8 GFC, with valid data bytes and special codes encoded into 10-bit Transmission Characters according to the 8B10B encoding.

3. [Network] A word-oriented transmission code specified by 10GFC, with 64 bits of data and special codes encoded into a 66-bit transmission unit according to the 64/66 encoding.

Transmission Control Protocol (TCP)

[Network] The Internet connection oriented network transport protocol, which provides a reliable delivery service.

transmission word

[Fibre Channel] A string of four contiguous transmission characters aligned on boundaries that are zero modulo 4 from a previously received or transmitted special character.

Fibre Channel transmission and reception operates in transmission word units when using 8B/10B encoding.


1. [Fibre Channel] The portion of a Link_Control_Facility that converts valid data bytes and special codes into transmission characters using the rules specified by the transmission code, converting these transmission characters into a bit stream, and transmitting this bit stream on an optical or electrical transmission medium.

2. [Fibre Channel] An electronic circuit that converts an electrical logic signal to a signal suitable for an optical or electrical communications media.

transparent failover

[Computer System] A failover from one component of a system to another that is transparent to the external operating environment.

Often used to refer to paired disk controllers, one of which exports the other’s virtual disks at the same host bus addresses after a failure. See non-transparent failover.

Transport Layer Security (TLS)

[Data Security] A protocol suite defined by the IETF that provides confidentiality and data integrity between two communicating applications.

TLS is composed of two layers: the TLS Record Protocol and the TLS Handshake Protocol. The TLS Record Protocol provides connection security with an encryption method (such as DES). The TLS Handshake Protocol allows peers (client and server) to authenticate each other as well as to negotiate an encryption algorithm and cryptographic keys before data is exchanged. The TLS protocol is standardized by the Internet Engineering Task Force (IETF) and is defined in several RFC documents. TLS is based on SSL, which was designed by Netscape Communications, but TLS and SSL are not interoperable. However, the TLS protocol does contain a mechanism that allows TLS implementations to back down to SSLv3.


[Management] A type of SNMP message used to signal that an event has occurred.

Trap delivery to recipients uses UDP and is not completely reliable. See best effort.

triaxial cable

[Network] An electrical transmission medium consisting of three concentric conductors separated by a dielectric material with the spacings and material arranged to give a specified electrical impedance.

See coaxial cable.

Triple DES (3DES)

[Data Security] A variant of the Data Encryption Standard (DES) in which the algorithm is applied three times in succession using two or three different keys.

trojan horse

[Data Security] Hidden code in a computer program that allows the unauthorized collection, falsification, or destruction of information.


[Data Security] Belief in the reliability, truth, ability, or strength of someone or something.

A trusted system is believed to have the ability to function as expected and to not misbehave.

Trusted Computing Group (TCG)

[Data Security] A not-for-profit organization formed to develop, define, and promote open standards for hardware-enabled trusted computing and security technologies, including hardware building blocks and software interfaces, across multiple platforms, peripherals, and devices.

trusted system

[Data Security] A system that may be used for processing of sensitive or classified information, that employs sufficient hardware and software integrity measures to assure that it performs according to its documented specification and acts in a predictable manner.

Such a system is developed in accordance with security criteria and evaluated by these criteria.


[iSCSI] Acronym for Target Session Identifying Handle.


[Data Security] A technology that enables one network protocol to send its data via another network protocol's connections.

Tunneling works by encapsulating the first network protocol within packets carried by the second protocol. A tunnel may also encapsulate a protocol within itself (e.g., an IPsec gateway operates in this fashion, encapsulating IP in IP and inserting additional IPsec information between the two IP headers).


[Standards] Acronym for Technical Working Group.

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