[Fibre Channel] The Source_ID, a three-byte field that contains the address identifier of the source Nx_Port.


[Data Security] Acronym for Security Association.


[Services] Acronym for Software as a Service.


[SCSI] Acronym for SCSI Architecture Model.

The SCSI Architecture Model is developed and owned by the T10 working group of ANSI. SAM has undergone numerous revisions, each being consecutively named as SAM-2, SAM-3 and so on, the latest revision being SAM-5.


1. [Fibre Channel] [iSCSI] [Network] Storage Area Network.

This is the normal meaning in SNIA documents.

2. [Computer System] Acronym for Server Area Network, which connects one or more servers.

3. [Computer System] Acronym for System Area Network, an interconnected set of system elements.


[Data Security] A process or method to sanitize.
[ISO/IEC 27040]


[Data Security] Render access to target data on storage media infeasible for a given level of effort. [ISO/IEC 27040]

Clear, purge, and destruct are actions that can be taken to sanitize storage media. See media sanitization.


[SCSI] Acronym for Serial Attached SCSI.

SAS Expander

[SCSI] Short for Serial Attached SCSI Expander.

SAS Protocol Layer (SPL)

[SCSI] The layer of the SAS interconnect that comprises the Serial SCSI Protocol (SSP), the Serial ATA Tunneled Protocol (STP) and the Serial Management Protocol (SMP).


[Storage System] Acronym for Serial Advanced Technology Attachment.

saturated disk

[Storage System] A disk whose instantaneous I/O load is as great as or greater than its capability to satisfy the requests comprising the load.

Mathematically, a saturated disk's I/O queue eventually becomes indefinitely long. In practice, however, user reaction or other system factors generally reduce the rate of new request arrivals for a saturated disk.


[Computer System] To grow or support growth in such a way that all capabilities of the system remain in constant ratio to each other.

A storage subsystem whose data transfer capacity increases by the addition of buses as its storage capacity increases by the addition of disks is said to scale.


1. [Management] A collection of information models or data models.

2. [Data Management] Data that describes the organization and format of other data.


[Data Communication] Modifying data by XORing each bit with a pattern generated by a linear feedback shift register to minimize repetitive character patterns.


1. [Storage System] A parameterized list of primitive I/O interconnect operations intended to be executed in sequence.

Often used with respect to ports, most of which are able to execute scripts of I/O commands autonomously (without policy processor assistance).

2. [Computer System] A sequence of instructions intended to be parsed and carried out by a command line interpreter or other scripting language.

Perl, VBScript, JavaScript and Tcl are all scripting languages. See Command Line Interface.


[SCSI] Acronym for Small Computer System Interface.

SCSI adapter

[SCSI] An adapter that connects an intelligent device to a SCSI interconnect.

See HBA, host bus adapter.

SCSI address

[SCSI] The full address used by a computer to communicate with a SCSI device, including an adapter number (required with computers configured with multiple SCSI adapters), and the target ID of the device.

SCSI addresses do not include logical unit number, because those are not used for communication.

SCSI Architecture Model (SAM)

[SCSI] An ANSI standard that defines the generic requirements and overall framework in which other SCSI standards are defined.

New generations of this standard are identified by a numeric suffix; for example the second generation standard is SAM2.

SCSI bus

[SCSI] Deprecated synonym for SCSI interconnect.

SCSI Device

[SCSI] The SAM-2 term for an entity that contains other SCSI entities.

For example, a SCSI Initiator Device contains one or more SCSI Initiator Ports and zero or more application clients.

SCSI Enclosure Services (SES)

[SCSI] A standard for management of environmental factors such as temperature, power, voltage, etc.

SCSI Initiator Port

[SCSI] The initiator endpoint of an I_T nexus.

SCSI interconnect

[SCSI] A serial or parallel interconnect that implements a SCSI transport standard.

The number of SCSI initiator ports and SCSI target ports which may be connected on a SCSI bus is dependent upon the particular transport standard. See initiator, target.

SCSI Media Changer Commands (SMC)

[SCSI] A standard for media changer devices (i.e., libraries).

SCSI Over PCI Express (SOP)

[SCSI] A protocol to transport SCSI operations over PCI Express.

SCSI Parallel Interface (SPI)

[SCSI] The family of SCSI standards that define the characteristics of the parallel version of the SCSI interface.

Several versions of SPI, known as SPI, SPI2, SPI3, etc., have been developed. Each version provides for greater performance and functionality than preceding ones.

SCSI port

[SCSI] The SCSI term for an entity in a SCSI Device that provides the SCSI functionality to interface with a service delivery subsystem or transport.

SCSI Stream Commands (SSC)

[SCSI] A standard for sequential-access devices (i.e., tape drives).

SCSI target port

[SCSI] The target endpoint of an I_T nexus.

SCSI Trade Association (STA)

[General] A trade association incorporated in 1996 to promote all forms of SCSI technology in the market.

See http://www.scsita.org/.


[Management] Acronym for Software Defined Data Center.


[Network] Acronym for Synchronous Digital Hierarchy.


[Storage] Shorthand for software-defined storage.

secret key

[Data Security] A key used in a symmetric cryptosystem to both encrypt and decrypt data.

The key must remain confidential to the using parties to ensure the security of the cryptosystem.


[Storage System] The unit in which data is physically stored and protected against errors on a fixed block architecture disk.

A sector typically consists of a synchronization pattern, a header field containing the block’s address, data, a checksum or error correcting code, and a trailer. Adjacent sectors are often separated by information used to assist in track centering. Most often, each sector holds a block of data. See disk block.

secure hash

[Data Security] An algorithm that generates a fixed-size digest from its input (e.g., a message).

The algorithm has the properties that different inputs are extraordinarily unlikely to yield the same digest, small changes in its input lead to large changes in its output, and it is computationally intractable to generate an input that yields the same digest as another given input.

secure multi-tenancy

A type of multi-tenancy that employs security controls to explicitly guard against data breaches and provides validation of these controls for proper governance. [ISO/IEC 27040]

Secure multi-tenancy exists when the risk profile of an individual tenant is no greater than it would be in a dedicated, single-tenant environment. In very secure environments even the identity of the tenants is kept secret. See multi-tenancy.

Secure Remote Password (SRP)

[Data Security] An authentication and key exchange system.

SRP is standardized by the Internet Engineering Task Force and described in RFC 2945.

Secure Sockets Layer (SSL)

[Data Security] A suite of cryptographic algorithms, protocols and procedures used to provide security for communications used to access the world wide web.

The characters "https:" at the front of a URL cause SSL to be used to enhance communications security. More recent versions of SSL are known as TLS (Transport Level Security) and are standardized by the Internet Engineering Task Force (IETF).

SSL is a predecessor of TLS and is considered a vulnerability if it is supported in a product.

See also SSL.

Security Association (SA)

[Data Security] A simplex "connection" that affords security services to the traffic carried by it.

To secure typical, bi-directional communication between two hosts, or between two security gateways, two Security Associations (one in each direction) are required. In IPsec, a security association is uniquely identified by a triple consisting of a Security Parameters Index (SPI), an IP Destination Address, and a security protocol identifier (Authentication Header or Encapsulating Security Payload).

security domain

[Data Security] A collection of people and systems under the control of a single authority, often with a single security policy.

security incident

[Data Security] A single or a series of unwanted or unexpected events that have a significant probability of compromising business operations and threatening information security.

security principal

[Data Security] A securely identified and verified entity.

security safeguards

[Data Security] The protective measures and controls that are prescribed to meet the security requirements specified for a system.

Safeguards may include but are not necessarily limited to: hardware and software security features, operating procedures, accountability procedures, access and distribution controls, management constraints, personnel security, and physical structures, areas, and devices. Also called safeguards (without the adjective).

security strength

[Data Security] A measure of the computational complexity associated with defeating the protection conveyed by a given cryptographic algorithm.

Security strength is often expressed as a number of bits.

Security Target (ST)

[Data Security] A set of security functional and assurance requirements and specifications to be used as the basis for evaluation of an identified product or system, most commonly associated with ISO 15408.

Self-contained Information Retention Format (SIRF)

[Long Term Retention] A self-describing container format, developed by the SNIA, appropriate for the long-term storage of digital information.

self encrypting drive

[Storage System] A type of self encrypting storage device.

self encrypting storage device

[Storage System] A storage device that has the native ability to encrypt all user data written to and decrypt the same data read from it, and that prevents access until a credential is supplied.

Tape drives, disk drives and other types of storage devices may all be designed to be self encrypting storage devices.

self-signed certificate

[Data Security] A public key certificate whose digital signature may be verified by the public key contained within the certificate.

The signature on a self-signed certificate protects the integrity of the data, but does not guarantee authenticity of the information. The trust of self-signed certificates is based on the secure procedures used to distribute them. [NIST SP 800-57 Part 1]

sensitive information

[Data Security] Information that could adversely affect the interest or the conduct of an organization’s business or activities, or the privacy to which individuals are entitled.

Sequence Identifier

[Fibre Channel] A number transmitted with each data frame in a sequence that identifies the frame as part of the sequence.


[Fibre Channel] A set of Fibre Channel data frames with a common Sequence_ID (SEQ_ID), corresponding to one message element, block, or Information Unit.

Sequences are transmitted from the sequence initiator to the sequence recipient.

sequence initiative

[Fibre Channel] A Fibre Channel signaling feature that designates which end of an exchange has authority to send the next sequence.

Sequence Initiator

[Fibre Channel] An Nx_Port that initiates a sequence and transmits data frames to a destination Nx_Port.

Sequence Recipient

[Fibre Channel] An N_Port or NL_Port that receives Data frames from a Sequence Initiator and, if applicable, transmits responses (Link Control frames) to the Sequence Initiator.

Sequence Status Block

[Fibre Channel] A data structure that tracks the state of a sequence.

Both Sequence Initiators and Sequence Recipients have Sequence Status Blocks for each active sequence.

sequential I/O
sequential I/O load
sequential reads
sequential writes

[Storage System] An I/O load consisting of consecutively issued read or write requests to adjacently addressed data.

Sequential I/O is characteristic of data transfer intensive applications. See random I/O.


[Computer System] Short for Serializer Deserializer.

serial (transmission)

[General] The transmission of data bits one at a time over a single link.

serial adapter

[Computer System] An adapter that connects an intelligent device to an RS232 or RS425 serial communications link.

Serial adapters are sometimes used by storage subsystems, filers, and other intelligent devices to connect to serial consoles for management purposes. See host adapter.

Serial Advanced Technology Attachment (SATA)

[Storage System] A version of the ATA interface that uses a serial connection architecture.

Serial Attached SCSI (SAS)

[SCSI] A SCSI interface standard that provides for attaching hosts to SCSI devices, including SAS and SATA disk and tape drives.

INCITS Technical Committee T10 is responsible for the national (ANSI) and international (ISO) standards for SAS. See www.t10.org.

Serial Attached SCSI Expander

[SCSI] A switching device that uses virtualization to allow multiple SAS devices to be connected to each initiator port.

serial console

[Computer System] A real or emulated communication terminal used by humans to manage an intelligent device.

Serial consoles connect to the devices’ virtual or physical serial adapters.

Serializer Deserializer (SERDES)

[Computer System] A mechanism for converting data from parallel to serial form and from serial to parallel form.


1. [Computer System] An intelligent device, usually a computer, that provides services to other intelligent devices, usually other computers or appliances. See client.

2. [Computer System] An asymmetric relationship with a second party (a client) in which the client initiates requests and the server responds to those requests.

server based virtualization

[Computer System] Synonym for host based virtualization.

Server Message Block (protocol) (SMB)

[Network] A network file system access protocol designed primarily used by Windows clients to communicate file access requests to Windows servers.

Current versions of the SMB protocol are referred to as CIFS, the Common Internet File System.

serverless backup

[Data Recovery] A backup methodology that utilizes a device other than the server to copy data without using the LAN.

The copy may be performed by a network-attached controller (e.g., utilizing SCSI Extended Copy), by an appliance within the SAN, or by a Backup Server.

Service Incident Standard (SIS)

[Management] A DMTF standard that defines how a support or help desk incident is processed.

Service Level Agreement (SLA)

[General] An agreement between a service provider, such as an IT department, an internet services provider, or an intelligent device acting as a server, and a service consumer.

A service level agreement defines parameters for measuring the service, and states quantitative values for those parameters.

Service Level Objective (SLO)

[General] A partition of an SLA consisting of individual metrics and operational information to enforce and/or monitor the SLA.

Service Level Objectives may be defined as part of an SLA, an SLS, or in a separate document. Each is a set of parameters and their values. The actions of enforcing and reporting monitored compliance can be implemented as one or more policies. See Service Level Agreement.

Service Location Protocol (SLP)

[Management] An IETF standards track protocol that provides a framework to allow networking applications to dynamically discover the existence, location, and configuration of networked services in enterprise networks.

service root

[Management] A particular resource that is directly accessed via the Redfish service entry point.

This resource serves as a starting point for locating and accessing the other resources and associated metadata that together make up an instance of a Redfish service.


1. [SCSI] Acronym for SCSI Enclosure Services.

2. [Standards] Acronym for Solution Exchange Standard.


[Fibre Channel] Abbreviation for Source Fabric_Identifier.


[Data Security] Acronym for Secure Hash.


[File System] A resource such as a data volume or a printer device made available for use by users on other computer systems.

For example, a printer or a collection of files stored in a single directory tree on a file server may be made available as a share. CIFS clients, which include most networked personal computers, typically map a share to a drive letter.

shared secret

[Data Security] A pre-shared key that has been distributed to communicating parties prior to beginning of an encrypted communication.


[Storage System] A modular enclosure for storage devices such as disks and tapes.

Storage shelves usually contain power supplies and cooling devices, and have pre-wired backplanes that carry power and I/O interconnect signals to the devices mounted in them. See canister.

shielded enclosure

[Data Security] A room or container designed to attenuate electromagnetic radiation.


1. [General] Acronym for Semiconductor Industries Association.

2. [SCSI] Acronym for SCSI Industry Association.

Simple Network Management Protocol (SNMP)

[Network] [Standards] An IETF protocol for monitoring and managing systems and devices in a network.

The data being monitored and managed is defined by a MIB. The functions supported by the protocol are the request and retrieval of data, the setting or writing of data, and traps that signal the occurrence of events.

single (component) configuration

[General] A configuration in which the referenced component is not redundant.

See redundant (component).

single ended (signaling)

[SCSI] An electrical signaling technique in which all control and data signals are represented by a voltage difference from a common ground.

See differential.

single instance storage

[Storage System] A form of data deduplication that operates at a granularity of an entire file or data object.

See data deduplication, subfile data deduplication.

single mode (fiber optic cable)

[Fibre Channel] [Network] A fiber optic cabling specification that provides for up to 10 kilometer distance between devices.

single mode fibre

[Fibre Channel] Optical fiber that is designed for the transmission of a single ray or mode of light as a carrier.

Single mode fibre transmission is typically used for long-distance signal transmission.

Single Point Of Failure (SPOF)

[General] One component or path in a system, the failure of which would make the system inoperable.

Single Sign On (SSO)

[Data Security] A form of centralized authentication employing a single set of credentials that are used transparently to perform subsequent authentications on behalf of the users.


[Long Term Retention] Acronym for Self-contained Information Retention Format.


1. [Management] [Standards] Acronym for Service Incident Standard.

2. [Storage System] Acronym for Single Instance Storage.


[General] Acronym for Service Level Agreement.


[General] Acronym for Service Level Objective.


[Management] Acronym for Service Location Protocol.

Small Computer System Interface (SCSI)

[SCSI] A collection of ANSI standards and proposed standards that define I/O interconnects primarily intended for connecting storage subsystems or devices to hosts through host bus adapters.

Originally intended primarily for use with small (desktop and desk-side workstation) computers, SCSI has been extended to serve most computing needs, and is arguably the most widely implemented I/O interconnect in use today.

small read request
small write request
small I/O request

[Storage System] An I/O, read, or write request that specifies the transfer of a relatively small amount of data.

‘Small’ usually depends on the context, but most often refers to 8 KBytes or fewer. See large I/O request.


[File System] [Network] Acronym for Server Message Block.


1. [Management] The Storage Networking Industry Association's (SNIA) Storage Management Initiative (SMI).

SMI develops and standardizes interoperable storage management technologies, including providing conformance testing for products.

2. [Fibre Channel] [Management] [Network] Acronym for Structure of Management Information.


[Standards] Acronym for Storage Management Initiative Specification.


[Standards] Acronym for Society of Motion Picture and Television Engineers.


[Data Management] A point in time copy of a defined collection of data.

Clones and snapshots are full copies. See delta snapshot. Depending on the system, snapshots may be of files, LUNs, file systems, or any other type of container supported by the system.


[Network] [Standards] [Storage System]

Acronym for Storage Networking Industry Association.


[Data Security] A software tool for auditing and identifying network traffic packets.


[Network] [Management] Acronym for Simple Network Management Protocol.


[Network] Acronym for Simple Name Server.

social engineering

[Data Security] Use of social rather than technical methods to obtain sensitive information or perform privileged actions.

Examples include tricking people into downloading and executing files that appear to be benign but are actually malicious, revealing passwords, etc.

Society of Motion Picture and Television Engineers (SMPTE)

[Standards] An industry association whose goal is to standardize television and motion picture industry information interchange protocols.


[Fibre Channel] Acronym for Start Of Frame.

soft link

[File System] Synonym for symbolic link.

soft zone

[Fibre Channel] A zone consisting of zone members that are permitted to communicate with each other via the fabric.

Soft zones are typically implemented through a combination of name server and Fibre Channel protocol — when a port contacts the name server, the name server returns information only about Fibre Channel ports in the same zone(s) as the requesting port. This prevents ports outside the zone(s) from being discovered and hence the Fibre Channel protocol will not attempt to communicate with such ports. In contrast to hard zones, soft zones are not enforced by hardware; e.g., a frame that is erroneously addressed to a port that should not receive it will nonetheless be delivered. Well-known addresses are implicitly included in every zone. See zone, hard zone.

software appliance

[Computer System] An application combined with an operating environment designed to run on industry standard hardware.

If a vendor installs the software appliance on hardware prior to customer delivery, the offering is considered an appliance.

Software as a Service (SaaS)

[Services] Delivery over a network, on demand, of the use of an application.

Software Defined Data Center (SDDC)

[Management] A virtualized data center with a service management interface.

Application requirements determine the service levels provided.

software-defined storage (SDS)

[Storage] Virtualized storage with a service management interface.

SDS includes pools of storage with data service characteristics that may be applied to meet the requirements specified through the service management interface.

solicited control

[Fibre Channel] An information category indicated in a Fibre Channel frame header.

solicited data

[Fibre Channel] An information category indicated in a Fibre Channel frame header.

solid state array

[Storage System] Synonym for solid state storage array.

Solid State Disk

[Storage System] Synonym for Solid State Drive.

Solid State Storage (SSS)

[Storage System] A storage capability built from solid state electronics.

solid state storage array

[Storage System] A storage array that uses solid state storage and may contain other storage media.

Solid State Drive (SSD)

[Storage System] A disk drive whose storage capability is provided by solid state storage.

Form factors and interfaces for solid state drives are typically the same as for traditional disk drives.

Solution Exchange Standard

[Management] A DMTF standard that defines the exchange of support or help desk information.

solution under test

[Computer System] All hardware and software components that are exercised during a test to verify functional behavior or determine performance characteristics.

The solution under test comprises the infrastructure including software components, application(s), test system(s), and the system(s) under test.

See also system under test and test system.


[Network] Shorthand for Synchronous Optical Network.

Source Identifier (S_ID)

[Fibre Channel] A number in a Fibre Channel frame that identifies the source of the frame.

See D_ID.

source N_Port

[Fibre Channel] The Nx_Port from which a frame is transmitted.

space reduction

[Storage System] Deprecated synonym for capacity optimization.

spare (disk, extent)

[Storage System] An object reserved for the purpose of substitution for a like object in case of that object's failure.

sparse file

[File System] A file that has empty (unwritten and unallocated) data regions, which on reading back are implicitly filled with bytes containing the value zero (0x00).

On some file systems all files are implicitly sparse.

special character

[Fibre Channel] Any transmission character that is valid in the transmission code but does not correspond to a valid data byte.

Special characters are used to denote special functions.

special code

[Fibre Channel] A code that, when encoded using the rules specified by the transmission code, results in a special character.

Special codes are typically associated with control signals related to protocol management (e.g., K28.5).


[SCSI] Acronym for SCSI Parallel Interface.

spiral data transfer rate

[Storage System] Synonym for full volume transfer rate.

split I/O request

1. [Storage System] An I/O request to a virtual disk that requires two or more I/O operations to satisfy, because the virtual data addresses in the request map to more than one extent on one or more disks.

2. [Storage System] An application I/O request that is divided into two or more sub-requests by a file system or other operating system component because the amount of data requested is too large for the operating environment to handle as a unit.

split mirror, split mirror copy
split mirror point in time copy

1. [Storage System] Any of a class of point in time copy implementations or the resulting copies in which the storage for the copy is synchronized to the source of the copy and then split.

A split mirror copy occupies as much storage as the source of the copy.

2. [Data Recovery] A method for generating a frozen image of a set of data.

A split mirror frozen image contains a complete copy of data as of the moment of frozen image creation. When a split mirror frozen image has served its purpose, it may be resynchronized with the original data from which it was split, or discarded.


[General] Acronym for Single Point Of Failure.

spoliation of evidence

[Legal] The intentional or negligent destruction, hiding, alteration, withholding or concealment of withholding of evidence relevant to a legal action.


[Data Security] Unauthorized use of legitimate identification and authentication data to mimic a subject different from the attacker.

Impersonating, masquerading, piggybacking and mimicking are forms of spoofing.


[Fibre Channel] Acronym for Sequence Recipient.


[Hardware] Acronym for Static Random Access Memory.


[Management] Acronym for Storage Resource Management.


[Data Security] Acronym for Secure Remote Password.


[Storage System] Acronym for Solid State Drive.


[iSCSI] Shorthand for iSCSI Session Identifier.


[Data Security] Acronym for Secure Sockets Layer.


[Data Security] Acronym for Single Sign On.


[Data Security] Acronym for Security Target.


[SCSI] Acronym for SCSI Trade Association.

stand alone drive

[Data Recovery] A removable media drive that is not associated with a media stacker or robot.

standard interconnect

[Standards] An I/O or network interconnect whose specifications are readily available to the public, and that can therefore easily be implemented in a vendor’s products without license or royalty payments.

Also called an open interconnect.


[Network] A physical network configuration in which every node is connected directly to, and only to, a central point; all communications pass through the central point, which may be a hub or a switch.

Start Of Frame (SOF)

[Fibre Channel] A group of ordered sets that delineates the beginning of a frame.

Static Random Access Memory (SRAM)

[Hardware] Byte-addressable computer memory that maintains state indefinitely given continuous power.


[General] A function that records data and supports retrieval.

Storage Area Network (SAN)

1. [Network] A network whose primary purpose is the transfer of data between computer systems and storage devices and among storage devices.

A SAN consists of a communication infrastructure, which provides physical connections, and a management layer, which organizes the connections, storage devices, and computer systems so that data transfer is secure and robust. The term SAN is usually (but not necessarily) identified with block I/O services rather than file access services.

2. [Storage System] A storage system consisting of storage elements, storage devices, computer systems, and/or appliances, plus all control software, communicating over a network.

The SNIA definition specifically does not identify the term SAN with Fibre Channel technology. When the term SAN is used in connection with Fibre Channel technology, use of a qualified phrase such as "Fibre Channel SAN" is encouraged. According to this definition, an Ethernet-based network whose primary purpose is to provide access to storage devices would be considered a SAN. SANs are sometimes also used for system interconnection in clusters.

storage array

[Storage System] A collection of storage devices from one or more commonly accessible storage subsystems, combined with a body of control software.

storage controller

[Storage System] A device for handling storage requests that includes a processor or sequencer programmed to autonomously process a substantial portion of I/O requests directed to storage devices.

Aggregating RAID controllers and filers are examples of storage controllers.

storage device

[Storage System] Any storage element or aggregation of elements, designed and built for data storage and delivery.

storage device virtualization

[Storage System] Virtualization of storage elements and storage devices such as disks, tape drives, RAID arrays, LUNs, file systems, etc.

storage domain

[Storage System] A collection of storage resources and supporting software and interfaces that are managed as a unit.

storage efficiency

[Storage System] The ratio of a storage system's effective capacity to its raw capacity.

An estimated efficiency calculation is permissible using estimated effective capacity.

The storage efficiency of a system is normally low when it is new. On a capacity optimizing system efficiency generally increases as the system is loaded with data. There is no way to precisely predict the storage efficiency of a loaded capacity optimizing system before data is loaded onto it.

storage element

[Storage System] Any component that is used to build storage devices and which contributes to persistent data storage and delivery, such as a disk drive, flash memory, tape, tape drive,, or library.

Storage elements are components of storage devices.

storage extent

[Storage System] A contiguous array of bytes—real or virtual—as exposed by a storage container.

A storage extent instance may include data on either removable or nonremovable media storage devices. See extent.

storage federation

[Storage System] Making multiple storage systems appear to a user as a single system.

Storage Interoperability

[Storage System] The ability of storage devices, products, or systems to work together in a correct, predictable and interchangeable fashion.

Storage Management Initiative-Specification (SMI-S)

[Management] [Standards] A storage management interface developed by SNIA, and standardized via ANSI and ISO.

storage media

[Storage System] The material in a storage device on which data is recorded.

Storage media includes electrical (e.g., solid state), magnetic (hard disk, tape), and optical media.

storage medium

1. [General] An individual that makes prophesies regarding the storage industry.

2. [Storage System] See storage media.

storage networking

[Storage System] [Network] The practice of creating, installing, administering, or using networks whose primary purpose is the transfer of data between computer systems and storage elements and among storage devices.

Storage Networking Industry Association (SNIA)

[Network] [Standards] [Storage System] A 501(c)(6) association of producers and consumers of storage networking products whose goal is to further storage networking technology and applications.

storage resource domain

[Management] The category of resources that encompasses storage services.

storage resource management

[Management] Management of physical and logical storage resources, including storage elements, storage devices, appliances, virtual devices, disk volume and file resources.

storage security

[Data Security] Application of physical, technical, and administrative controls to protect storage systems and infrastructure as well as the data stored (3.50) within them. [ISO/IEC 27040]

Storage security is focused on protecting data (and its storage infrastructure) against unauthorized disclosure, modification, or destruction while assuring its availability to authorized users. These controls may be preventive, detective, corrective, deterrent, recovery, or compensatory in nature.

storage service

[Management] A set of functions that provide storage.

storage subsystem

[Storage System] An integrated collection of (a.) storage controllers and/or host bus adapters, (b.) storage devices, CD-ROM drives, tape drives, and libraries, and (c.) any required control software, that provides storage services to one or more computers.

storage system power efficiency

[Storage System] The power efficiency of a storage system, where input power is measured at the wall socket and output power is measured at the power inputs to the disks, fans, robotics and electronics.

Measurement points of interest include the idle and maximum activity states.

storage taxonomy

[Standards] A hierarchical categorization of storage networking products based on capacity, availability, port count and other attributes.

The SNIA Emerald™ Power Efficiency Measurement Specification presents a storage taxonomy.

storage tier

[Storage System] Storage space that has availability, performance, and cost characteristics that justify the movement of data between it and other storage tiers based on the requirements of the stored data.

storage virtualization

1. [Storage System] The act of abstracting, hiding, or isolating the internal function of a storage (sub) system or service from applications, compute servers or general network resources for the purpose of enabling application and network independent management of storage or data.

2. [Storage System] The application of virtualization to storage services or devices for the purpose of aggregating, hiding complexity or adding new capabilities to lower level storage resources.

Storage can be virtualized simultaneously in multiple layers of a system, for instance to create HSM like systems.

store and forward (switching)

[Fibre Channel] [Network] A switching technique that requires buffering an entire frame before it is routed.


1. [Network] Continuous media content served over a specialized protocol in real-time.

2. [File System] A subfile in the CIFS protocol.

NFSv4 provides equivalent functionality using Named Attributes.

streamed sequence

[Fibre Channel] A new sequence initiated by a Sequence Initiator in any class of service for an exchange while it already has sequences open for that exchange.


[Storage System] The consecutively addressed blocks in a single extent.

A disk array’s controller uses strips to map virtual disk block addresses to member disk block addresses. Also known as stripe element.

strip size

[Storage System] Synonym for stripe depth.


[Storage System] The set of strips at corresponding locations of each member extent of a disk array that uses striped data mapping.

The strips in a stripe are associated with each other in a way (e.g., relative extent block addresses) that allows membership in the stripe to be quickly and uniquely determined by a computational algorithm. Parity RAID uses stripes to map virtual disk block addresses to member extent block addresses.

stripe depth

1. [Storage System] The number of blocks in a strip in a disk array that uses striped data mapping.

2. [Storage System] The number of consecutively addressed virtual disk blocks mapped to consecutively addressed blocks on a single member extent of a disk array.

stripe element

[Storage System] Synonym for strip.

stripe size

[Storage System] The number of blocks in a stripe.

A striped array’s stripe size is the stripe depth multiplied by the number of member extents. A parity RAID array’s stripe size is the stripe depth multiplied by the number of member extents less the number of parity extents.

striped array
striped disk array

[Storage System] A disk array with striped data mapping but no redundancy for failure protection.

Striped arrays are sometimes used to improve I/O performance on data that is of low value or easily replaced. Virtualizers may also use simple striping of the extents that they import, on the grounds that the underlying storage is responsible for data protection.


[Storage System] Synonym for striped array.


1. [Storage System] Short for data striping.

Also known as RAID Level 0 or RAID 0, striping is a mapping technique in which fixed-size consecutive ranges of virtual disk data addresses are mapped to successive array members in a cyclic pattern.

2. [Storage System] A network technique for aggregating the bandwidth of several links between the same pair of nodes.

A single data stream can be spread across the links for higher aggregate bandwidth. Sometimes called port aggregation.

Structure of Management Information (SMI)

[Fibre Channel] [Management] [Network] A notation for setting or retrieving management variables over SNMP.

SNMP queries are in the form of GET requests for one or more Object IDs (OIDs), which take the form; an encoding called ASN.1 is used to transmit both request and reply. The SMI spec—not to be confused with the SNIA's Storage Management Initiative—specifies the schema used in the OID strings.

structured data

[Data Management] Data that is organized and formatted in a known and fixed way.

The format and organization are customarily defined in a schema. The term structured data is usually taken to mean data generated and maintained by databases and business applications.


[File System] A directory in a hierarchical directory tree whose parent is a directory.

subfile data deduplication

[Storage System] A form of data deduplication that operates at a finer granularity than an entire file or data object.

See data deduplication, single instance storage.


[Data Security] In the context of access control or authorization, an entity whose access or usage is controlled.


[General] The assumption of a component's function in a system by a functionally equivalent component.

subtractive routing method

[SCSI] A method used by SAS expanders that forwards connection requests for unknown (i.e., not directly attached) devices via special designated phy links to another more authoritative expander.

The more authoritative expander is usually, but does not have to be, the "root" expander.


[Computer System] Shorthand for solution under test.


[Network] Acronym for Switched Virtual Circuit.


[General] The installation of a replacement unit in place of a defective unit in a system.

Units are any parts of a system that may either be field replaceable (FRUs) by a vendor service representative or consumer replaceable (CRUs). A physical swap operation may be cold, warm, or hot, depending on the state in which the disk subsystem must be in order to perform it. A functional swap operation may be an auto swap or it may require human intervention.


[Fibre Channel] [Network] A network infrastructure component to which multiple ports attach.

Unlike hubs, switches typically have internal bandwidth that is a multiple of link bandwidth, and the ability to rapidly switch port connections from one to another. A typical switch can accommodate several simultaneous full link bandwidth transmissions between different pairs of ports. See hub.


[Computer System] Synonym for failback.


[Computer System] Synonym for failover.


[Fibre Channel] A Name_Identifier that is associated with a Fibre Channel switch or bridge name.

switched over (system)

[Computer System] Synonym for failed over.


[Storage Management] A SNIA open standard for managing data and storage services.

Swordfish is an extension of the Redfish specification that enables simple, scalable, and interoperable management of storage resources, ranging from direct attached storage to complex enterprise class storage servers.

Swordfish service

[Storage Management] A Redfish service that conforms to requirements of the Swordfish specification.

Swordfish service entry point

[Storage Management] A Redfish service entry point through which a particular instance of a Swordfish Service is accessed.

symbolic link

[File System] A special type of file that can be used to redirect a file or directory path transparently to another file or directory that may be on another system.

Also known as symlink or soft link. Symbolic links differ from hard links in that deletion of the underlying file causes them to be "broken", and subsequent attempts to traverse them fail.


[File System] Shorthand for a symbolic link.

symmetric cryptography

[Data Security] Cryptography that uses a symmetric cryptosystem.

symmetric cryptosystem

[Data Security] A cryptographic algorithm in which the same key is used to encrypt and decrypt a single message or block of stored information.

Keys used in a symmetric cryptosystem must be kept secret, yet are required on both ends of a protocol exchange. They are commonly used on a per-session basis by layered protocols such as TLS and SSL.

symmetric virtualization

[Computer System] Deprecated synonym for in-band virtualization.


1. [Fibre Channel] A receiver's identification of a transmission word boundary.

2. [General] The act of aligning or making two entities be equivalent at a specified point in time.


[Data Management] In the context of data replication, to establish an identical copy of the user data on the primary volume onto the secondary volume.

Synchronous Digital Hierarchy (SDH)

[Network] A common worldwide telecommunications methodology, standardized by ISO with 155, 622, 2048 and 9953 Mbps serial data rates in steps of 4.

An SDH uses a light scrambling of data to remove only the lowest frequency elements with the goal of achieving maximum digital bandwidth use.

synchronous mirroring

[Storage System] Deprecated synonym for synchronous replication.

synchronous operations

[Computer System] Operations that have a fixed time relationship to each other.

Most commonly used to denote I/O operations that occur in time sequence, i.e., a successor operation does not occur until its predecessor is complete.

Synchronous Optical Network (SONET)

[Network] A standard for optical network elements and transmission.

SONET provides modular building blocks, fixed overheads, integrated operations channels, and flexible payload mappings. Basic SONET provides a bandwidth of 51.840 megabits/second. This is known as OC-1. Higher bandwidths that are n times the basic rate are available (known as OC-n). OC-3, OC-12, OC-48, and OC-192 are currently in common use.

synchronous replication

[Storage System] A replication technique in which data must be committed to stable storage at both the primary site and the secondary site before the write is acknowledged to the host.

system board

[Computer System] A printed circuit module containing mounting devices for processor(s), memory, and adapter cards, and implementing basic computer functions such as memory access, processor and I/O interconnect clocking, and human interface device attachment.

system disk

[Computer System] The disk on which a computer system's operating software is stored.

The system disk is usually the disk from which the operating system is bootstrapped (initially loaded into memory). It frequently contains the computer system's swap and/or page files as well, and may also contain libraries of common software shared among several applications.

system portability

[Computer System] The ability of a service, application or system to run in more than one environment.

system under test

[General] An entity being tested to verify functional behavior or determine performance characteristics.

See also solution under test and test system.