Glossary

Accelerator: a device, either internal or external, that reduces the I/O bottlenecks of conventional spinning disk drives through the addition of a solid-state drive or other managed cache.

Access Control: a storage management service that allows or prohibits the use of a resource.

Accessibility: the quality of being at hand, or available, when a service request is made or needed.

Address: comprised of a row address and a column address, the row address identifies the page and block to be accessed; the column address identifies the byte or word within a page to access.

Aggregators: a system that allows multiple NASs to be consolidated or combined onto a single (usually SAN) architecture; and they are used in support of data migration. Aggregators may be in-band, out-of-band, or a hybrid combination of both.

Ancillary Data Sets: additional representations of information, sometimes as metadata, that are contained in the nonpicture areas of a digital video frame or field. The data may include Dolby audio metadata, close caption information, and timecode. Digital video calls the information held in the horizontal and vertical data spaces, respectively, as HANC (horizontal ancillary data) and VANC (vertical ancillary data).

Anisotropic Magnetoresistive (AMR): the full proper name for magnetoresistive properties.

Arbitration: beginning process in the SCSI data access protocol and operations.

Archiving: the process of moving data assets from short-term media (e.g., disk storage) to a more permanent and infrequently accessed media (e.g., data tape).

Areal Density: the volume of data capable of being stored in a given amount of hard disk platter space.

Array: a grouping of disk drives to form a single logic device that may appear as a single volume (depending on how it is configured).

Atomic: all changes are made, that is, they are committed or there are no changes (none) made.

Atomic Consistent Isolated Durable (ACID): utilized in transaction database systems.

Attribute: a specification defining a property of an object, an element, or a file. An attribute may also refer to set the specific value for a given instance. It is a general specification for objects that may or may not be associated to a file attribute.

Automated Tape Library (ATL): a system comprised of data tape cartridges, tape drives, a robotically controlled tape manipulator, and associated software and hardware that is used for data archiving and storage management.

Autonomous Agent: a system situated within an environment that senses and then acts on that environment in pursuit of its own agenda over time.

Availability: the degree to which a system is operable, in a committable state. (see also “uptime”).

Backup: a protective measure for the short-term protection of assets kept on magnetic media.

Benchmark: a reference point, but one that is not necessarily a tool for planning capacity.

Betacam and Betacam SP: the analog component videotape format from Sony, which dominated the half-inch cassette based professional recording industry until digital recording emerged. A higher grade metal-oxide version (Betacam SP for “superior performance”) was also offered beginning around the mid-1980s.

Bit Depth: the number of bits (usually 8, 10, or 12 bits) representing the uniformly quantized (linear) sampling of the analog video (or audio signal) sets during the conversion to a digital bit stream.

Bit Flipping: when a bit changes from one state (“0”) to another (“1”) on its own.

Bit-Patterned Recording (BPR): an approach for extending the data densities in disk drives.

Block: a block is the smallest addressable unit for erase operations; in solid state of flash memory it consists of multiple pages.

Block Error Rate (BLER): a measure of the average number of raw channel errors when reading or writing CD type media. BLER is a measure of the number of data blocks per second that contain detectable errors at the input of the decoder.

Block Management: an error management technique; it is typically handled in the file system. The SSD (solid state disk) has shown value in supporting the migration of this operation from the file system to SSD.

Broadcast Frame: in reference to a networking system, is also known as a broadcast packet, like multicast, the frame or packet address specifies all computers on a network.

Bus Sniffing: (also bus snooping) a technique used in distributed shared memory systems and multiprocessors to achieve cache coherence.

Cache Coherence: the application of coherency when applied to sets of caches.

Capacity: the volume of bits (usually in gigabytes) that a store has or could reach.

Catalog: the index of those assets arranged per uses which support the media asset management services.

Chroma: relating to the color signals of the video signal, designated as “C.”

Chronology of Disk Drive Development:First Hard Disk (1956): IBM’s RAMAC is introduced. It has a capacity of about 5 Mbytes, stored on 50 24-in. disks. Its areal density is a mere 2000 bits/in.2 and its data throughput 8800 bits/second.

First Air Bearing Heads (1962): IBM’s model 1301 lowers the flying height of the heads to 250 microinches. It has a 28-Mbyte capacity on half as many heads as the original RAMAC and increases both areal density and throughput by about 1000%.

First Removable Disk Drive (1965): IBM’s model 2310 is the first disk drive with a removable disk pack. Many PC users believe removable hard disks as being a modern invention; in fact, they were very popular in the 1960s and 1970s.

First Ferrite Heads (1966): IBM’s model 2314 is the first hard disk to use ferrite core heads, the first type later used on PC hard disks.

First Modern Hard Disk Design (1973): IBM’s model 3340, nicknamed the “Winchester,” is introduced. With a capacity of 60 Mbytes, it introduces several key technologies that lead to it being considered by many the ancestor of the modern disk drive.

First Thin-Film Heads (1979): IBM’s model 3370 is the first with thin-film heads, which would for many years be the standard in the PC industry.

First 8-in. Form Factor Disk (1979): IBM’s model 3310 is the first disk drive with 8" platters, greatly reduced in size from the 14-in. that had been the standard for over a decade.

First 5.25-in. Form Factor Disk (1980): Seagate’s ST-506 is the first drive in the 5.25-in. form factor used in the earliest PCs.

First 3.5-in. Form Factor Disk Drive (1983): Rodime introduces the RO352, the first disk drive to use the 3.5-in. form factor, which became one of the most important industry standards.

First Expansion Card Disk Drive (1985): Quantum introduces the Hardcard, a 10.5-Mbyte hard disk mounted on an ISA expansion card for PCs that were originally built without a hard disk. This product places Quantum “on the map” so to speak.

First Voice Coil Actuator 3.5-in. Drive (1986): Conner Peripherals introduces the CP340, the first disk drive to use as a voice coil actuator.

First 2.5-in. Form Factor Disk Drive (1988): PrairieTek introduces a drive using 2.5-in. platters. This size later became a standard for portable computing.

First Low-Profile 3.5-in. Disk Drive (1988): Conner Peripherals introduces the CP3022, which was the first 3.5-in. drive to use the reduced 1-in. height, now called “low profile” and the standard for modern 3.5-in. drives.

First Drive Use of Magnetoresistive Heads and PRML Data Decoding (1990): IBM’s model 681 (Redwing), an 857-Mbyte drive, is the first to use MR heads and PRML.

First 1.8-in. Form Factor Disk Drive (1991): Integral Peripherals’ 1820 is the first hard disk with 1.8-in. platters, later used for PC Card disk drives.

First Thin-Film Disk (1991): IBM’s “Pacifica” mainframe drive is the first to replace oxide media with thin-film media on the platter surface.

First 1.3-in. Form Factor Disk Drive (1992): Hewlett-Packard’s C3013A is the first 1.3-in. drive.

First 1-Tbyte Hard Disk Drive (2007): Hitachi introduces the first 1-Tbyte hard drive.

First 2-Tbyte Hard Disk Drive (2009): Western Digital launches world’s first 2-Tbyte hard drive.

Highest Areal 3.5-in. Density Drive (2010): Seagate ships 3.5-in. desktop hard drive with world’s highest areal density.

Highest Areal Density 2.5-in. Drive (2010): Toshiba introduces industry’s highest areal density 2.5-in 750-Gbyte hard disk drive, model MK7559GSXP HDD, featuring an areal density of 839.1 Mbits/mm² (~542 Gbits/in.2).

First 3-Tbyte Hard Disk Drive (2010): Seagate breaks capacity ceiling with world’s first 3-Tbyte external desktop drive.

Class: a construct that is used as a template (or blueprint) to create objects of that class. A class has both an interface and a structure and describes the state and behavior that the objects of the class all share. A class is a cohesive package consisting of a particular kind of metadata (refer also to metaobject).

Clip Server: a device consisting of encoding and/or decoding components, storage, control and application(s) for the recording and playout of short segments (“clips”) of moving video or still images, sometimes with audio.

Clustering: the grouping of servers and/or other resources that appear to a client as a single system.

Codec: a portmanteau of the words “compressor–decompressor” or “coder–decoder.”

Coding: those processes used in converting a signal from one format to another in computer science; when representing video data, for storage and/or transmission, this may involve either analog or digital video.

Coherence: the behavior of reads and writes to the same memory location.

Color Difference Signals: the video signal sets derived after the RGB signals are matrixed into a new set that uses luma (Y) as the base, and the differences between luma and other color information that originated from the RGB signal set.

Collaboration: when multiple uses share common resources on similar or different activities.

Component Digital Recording: known as D-1, the full bandwidth, 4:2:2 10-bit linear recording format using 19-mm videotape popular in the 1990s.

Composite Digital Recording: the D-2 and D-3 linear tape formats using 4fSC sampling (NTSC) produced by Ampex, Sony, and Panasonic.

Connection: communications between the initiator and target, which occurs over one or more TCP connections. The TCP connections carry control messages, SCSI commands, parameters, and data within iSCSI Protocol Data Units (iSCSI PDUs).

Connection ID (CID): connections within a session are identified by a unique ID that is generated by the initiator and presented to the target during login requests and during logouts that close connections.

Consistent: In a database system, the transaction will not violate declared system integrity constraints (see also “atomic”).

Container: an object that can contain other objects.

Content: media information typically without the additional elements of descriptive or structural metadata.

Content Distribution Network (CDN): a system built around an IT network that carries files between one location (or system) and another, typically built of proprietary software that manages a closed or open network.

Contention: a quality of service issue in storage systems caused by excessive collisions or requests for I/O that degrades overall system performance.

Conversion: any process that changes one state of a file or audio/video stream to another format, as in analog-to-digital conversion.

Copy-Back: see “write-back.”

Core Switch: provides the primary data paths across a fabric and the direction connections to the storage devices.

Data Deduplication: a method for mitigating storage capacity limitations by eliminating all redundant data in a storage system and replacing the differentiated (duplicated) data with only pointers.

Data Mover: a component, typical to an archive system, which handles the migration of files from one storage platform to another.

Data Object: a representation of some structured data.

Data Wrangling: the first stage of the data pipeline leading from the operational sources to the final user interfaces. Parenthetically, one will lasso the data and get it under our control; successfully including data capture, extraction, data staging, archiving and the first stage of data warehouse compliance.

Decoder: the electronic components and software that changes the digital bit stream back to a moving or static image or sound.

Defragmentation: the process of combining data segments that are scattered about a hard disk into contiguous groups so as to reduce latency or to allow that data to be accessed faster (by placing it closer to the fastest access tracks on the drive).

Delta Differencing: (also called “delta differential”) a process of examining a backup file set and locating the blocks or bytes that have changed, since the last backup period, and then only backing up those changes.

Digital Betacam: Sony’s digital equivalent of the analog Betacam SP format.

Digital Disk Recorder (DDR): a hard disk–based video and audio recording, storage, and playout platform.

Digital Video Recorder (DVR): an alternative nomenclature for a digital disk recorder (DVR).

Digital S: the market name for a cassette-based digital video recording platform that was standardized as D-9 by SMPTE in 1999.

Direct Access Storage Device (DASD): a longer name for direct-attached storage (DAS).

Disc: a removable optical media such as a CD, DVD, or Blu-ray Disc.

Disk: referring to magnetic media, including the outdated floppy disk, a computer’s magnetic spinning hard drive, external hard drives, and the storage components of a disk array.

Disk Mirroring: when identical drives have identical data simultaneously recorded to them, and when accessed, produce simultaneous read-backs (also called “shadowing”).

Disk Striping: a mechanism to divide the data in a file into segments that are scattered over the individual drives of a disk array.

Document Structuring Conventions (DSC): a set of standards for PostScript, based on the use of comments, which primarily specifies a way to structure a PostScript file and a way to expose that structure in a machine-readable way. A PostScript file that conforms to DSC is called a conforming document.

Dye Sublimation: a manufacturing process used in making DVDs and associated duplication that employs heat to transfer dye onto a medium such as a plastic card, paper, or fabric.

Downtime: the period when a system is not usable, often because of failure, maintenance, or upgrading.

Duplexing: another name for disk mirroring, also called shadowing.

Durable: in a transaction database, committed changes survive various classes of hardware

failure.

DV/DVCAM: the professional and consumer formats for video recording introduced in the mid-1990s with a data rate of 25 Mbits/second.

DVCPRO: Panasonic’s cassette-based digital video recording platform for both standard definition and high definition.

Edge Switch: at the periphery of the fabric, this device provides direct connections to host servers and management workstations.

E-Discovery: (also written eDiscovery) short for “electronic discovery,” referring to the processes in legal circles where electronic data is searched, located, and secured as evidence in a civil litigation proceeding.

Electronically Programmable Read-Only Memory (EPROM): a solid-state device that predates the uses of flash memory, which was a fundamental element of a computer where the BIOS or other important pieces of “firmware” would be kept.

Encoder: the electronic components and software that change a moving or static image or sound into a digital bit stream.

End-of-Life (EOL): the point where the recovery or playback device is no longer capable of recovering meaningful data from that media, or  when a product is no longer made or supported by the manufacturer.

Enhanced Small Disk Interface (ESDI): developed in the early 1980s by Maxtor Corporation that migrated control components directly to the disk drive chassis.

Error Correction Code (ECC): additional information added to data to allow errors to be detected and possibly corrected.

Essence: the raw audio, video, or data.

Extensible Markup Language (XML): a simple, very flexible text format derived from SGML (ISO 8879); XML is playing an increasingly important role in the exchange of a wide variety of data on the Web and elsewhere.

Fabric: one or more Fibre Channel (FC) switching devices that interconnect on N_ports and router FC frames.

Fault Tolerance: the ability of a system to respond gracefully to an unexpected failure in hardware or software.

Fibre Channel: a gigabit networking technology used extensively in high-performance storage that is standardized in the T11 Technical Committee of the ANSI accredited International Committee for Information Technology Standards (INCITS).

Fibre Channel: the integrated set of ANSI standards that define new protocols for the information transfer and is a high-performance serial data channel.

File Allocation Table (FAT): a table that centralizes the information about which areas of a disk drive belong to files, which are either free or unusable, and where each file is stored on the disk.

File Attribute: metadata describing or associating with a block of arbitrary information, usually a computer file. Attributes are used to track information about the file or the object; for example, the date a file was created and last modified, the file size, its extension and other properties such as permissions or rights.

File System in User Space (FUSE): a loadable kernel module for Unix-like computer operating systems that allows nonprivileged users to create their own file systems without editing the kernel code. The code runs in user space, as does LTFS (Linear Tape File System) that also runs in this user space on LTO-5 (and later) generation media.

FireWire: Apple's trademarked name for their IEEE 1394 interface available at 400 Mbits/second as FireWire 400 (IEEE 1394) and 800 Mbits/second as FireWire 800 (IEEE 1394b).

Flash (Memory): a nonvolatile chip that can be electrically erased and reprogrammed; flash may be found capitalized (Flash) or not (flash).

Format: a particular set of encoder and/or decoder components (codecs) plus a set of containers (or wrappers), which may be either platform agnostic (i.e., platform independent) or platform dependent (i.e., platform specific).

Frame: the set of fields that make up a unit of transmission, similar to a packet found in IP/Ethernet.  A frame in video is a single element image in a sequence of moving video, which can be a standalone image (as in progressive formats) or a combination of fields (as in interlaced formats.)

Free Space Fragmentation: referring to when the empty space on a disk is broken into small sets of scattered segments that are randomly distributed over the medium.

Full-Bandwidth: the term applied to video that has not been compressed, as in standard-definition digital (SD) at 270 Mbits/second in SMPTE 259M or high-definition digital (HD) at 1.485 Gbits/second in SMPTE 292M.

Gateway: a network point that acts as an entrance to another network. A gateway is often associated with both a router (which knows where to direct a given packet of data that arrives at the gateway) and a switch (which provides the actual path in and out of the gateway for a given packet).

Giant Magnetoresistance (GMR): a process whereby the fields of magnetism on the surface of a drive are much larger than in the MR process.

Hash Collision: occurs when a hash algorithm produces the same hash number for two different chunks of data, resulting in a false positive situation.

Heterogeneous Storage Architectures: storage elements that have been provided by

different vendors and that can be installed to work together.

HDCAM: Sony’s cassette-based digital video camcorder and transport series for high-definition television.  Also HDCAM SR, the higher resolution, higher data rate format used frequently by the video motion picture industry.

HDi (formerly iHD): Microsoft’s implementation of the Advanced Content interactivity layer in HD DVD, which was once used in the Xbox 360 HD DVD add-on, as well as stand-alone HD DVD players.

HDV: the high-definition video format based on the DV cassette tape developed by Sharp, Sony, and JVC successfully placed in both the professional and the consumer marketplaces.

Hierarchical Storage Management (HSM): an automatic way of managing and distributing data between different storage tiers (layers) to meet user needs for accessing data.

High Availability: the relative speed of access that a storage system has.

i.LinkTM: the trademark for the standard IEEE 1394 digital transfer protocol. The Sony i.LINKTM uses copy protection technology licensed by the Digital Transmission Licensing Administrator (DTLA), making it possible to handle a wide variety of digital video and audio signals while safeguarding copyrights.

Information: data that has meaning.

Initiator: the device that originates the signal or inquiry.

Input/Output Operations Per Second (IOPS): a benchmark used to describe performance in storage devices; they are not necessarily providing actual performance in application specific environments.

Instance: an object of a given class.

Interface: a set of named operations invoked by clients and generally referring to an abstraction (the reduction or factoring out of details) that an entity provides of itself to the outside. An interface may be information that a metaobject might store related to a base object.

Interoperable: the ability of diverse systems to work together (i.e., to interoperate).

Inter-Switch Link: a physical E_port between switches in a FC fabric.

Isolated: in a transaction database, the results are independent of concurrent transactions.

Journaling: the process of chronologically entering or recording information so that it can be sequentially recalled. In a file system, journaling is used (in various methods) to allow for the graceful recovery to a previous condition should a crash or power failure disable the operating system.

Just a Bunch of Disks (JBOD): an arrangement of hard disks that employs serial addressing

from the host port of a device. This configuration is not an official RAID set.

Lands: the area between each pit on an optical disc’s surface.

Luma: relating to the intensity of the noncolor elements in a video signal, that is, the “colorless” video channel, designated as “Y.”

Lossless Codec: will typically be used to remove unnecessary data during a compression process while retaining all of the information present in the original stream. Note: Using more than one codec or encoding scheme successively can also degrade quality significantly. The decreasing cost of storage capacity and network bandwidth has a tendency to reduce the need for lossy codecs for some media.

Lossy Codec: a codec that will remove information and reduce image quality by some degree in order to achieve the desired compression level. Repeating the encoding and decoding of an image using a lossy codecs will degrade the quality of the resulting data such that the image is no longer identifiable.

Master File Table (MFT): The MFT is part of the NT file system which keeps track of all the files on a disk. There is one MFT for every NT disk. Fragmentation of the MFT can seriously impact performance, as the operating system has to go through the MFT to retrieve any file on the disk.

Master Key: (also called “top key”), highest level of a key management system for security or encryption. Master keys should only be offline and only accessible by the drive owner (i.e., the system administrator).

Matrix: the mathematical principles that are used to proportionately combine the RGB signals and form them into new signals, such as Y'C'BC'R or Y'P'BP'R.

Mebibyte (MiB): a multiple of the unit byte for digital information, established by the International Electrotechnical Commission (IEC) in 2000. The binary prefix “mebi” means 220. A single mebibyte (1 MiB) is 1,048, 576 bytes. This designation is intended to replace the megabyte used in certain computer science contexts to mean 220 bytes (which conflicts with the SI definition of the prefix “mega”).

Media Asset: the components that include essence and metadata.

Media Asset Management: the processes, software and systems associated with the control, location, and referencing of media assets (those the components that include essence and metadata).

Media Information Object: information prior to becoming an asset, that is, a component which only presents information.

Message Digest: also referred to as a checksum or a hash, is a mathematical function that processes information so as to produce a different message digest for each unique document. Identical documents have the same message digest. Common message digest algorithms include CRC-32, MD5, RIPEMD-160, SHA, and HAVAL.

Metadata: information about the data, the “data about the data” or the “bits about the bits.”  In a media centric system, metadata usually refers to any set of ancillary information or data that is related to the essence, but is not the actual audio, video or data set (e.g., timecode) itself.

Metafile: a software file that describes how information such as essence, data, and metadata are stored but does not describe how the information is coded.

Metalanguage: alternative name for metadata, in some spaces the syntax or language associated with metadata.

Metaobject: in computer science, any entity that manipulates, creates, describes, or implements other objects. The base object is the object that the metaobject is about.

Meta Tag: machine parsable metadata about an HTML document which is not typically displayed.

MII Format: the analog component half-inch cassette-based professional recording videotape format from Panasonic (formerly Matsushita Electric Industrial), which competed with Sony’s Betacam format.  (MI was its short lived predecessor)

Multichannel Video Program(ming) Distributor (MVPD): an entity (service provider) that assembles programs for distribution over cable, satellite, or a network (e.g., IPTV) as a service.

Multilevel Cell (MLC): in flash, a form of memory that can store more than one bit per cell by choosing between multiple levels of electrical charge that can be applied to the floating gates of its cell.

NAND: a form of flash memory that is available in two types, single-level cell (SLC) or multi-level cell (MLC).

NAS Sprawl: a condition when multiple sets of network-attached storage devices overburden IT administrators from a management and control perspective to the point that performance is degraded.

Native: full bandwidth, uncompressed data storage on tape.  The natural and basic format of the file, video or audio essence or data itself which is unaltered from its original state.

Network Address Authority (NNA): a naming format defined by the INCITS T11 Fibre Channel protocols (FC-FS).

Network Entity: represents a device or gateway that is accessible from the IP network. A Network Entity must have one or more Network Portals, each of which can be used to gain access to the IP network by some iSCSI Nodes contained in that Network Entity.

Network Portal: a component of a Network Entity that has a TCP/IP network address and that may be used by an iSCSI Node within that Network Entity for the connection(s) within one of its iSCSI sessions. A Network Portal in an initiator is identified by its IP address. A Network Portal in a target is identified by its IP address and its listening TCP port.

Node: a connection point in a network, functioning either as a redistribution point or an end point for data transmissions. A node usually has the capability to recognize and then process, or forward, transmissions to other nodes.  Also considered an endpoint, connection point or an intersection point in a system.

Nonlinear Editing (NLE): the process of assembling source material content that is accessed in a random basis using a computer or desktop workstation from files typically stored on a disk or solid-state storage.  The term was given to the successor of the “off-line” editing process, most commonly employing digitized compressed video on a timeline editor via a display-based graphical user interface (GUI). The term was made most popular by Avid Technology (Burlington, MA) with its introduction of the Media Composer platform in the 1990s.

Nonvolatile Memory: a form of storage that retains its state (as a 1 or 0) when power is removed.

NOR: a form of flash memory based on the NOR gate (NOR meaning the Boolean term “not-OR).

Object: in computer science, any entity that can be manipulated by the commands of a programming language. Entities include such items as value, variable, function, or data structure.

Object-Based Storage (OBS): a protocol layer that is independent of the underlying storage hardware.

Object-Based Storage Device (OSD): a computer storage device, similar to disk storage, but intended to work at a higher level.

Objects in Computer Science—Terminologies Compared: the technology of object-based computer science is not formally covered in this book; however, given that the concepts surrounding object-based storage and associated devices grew from the computer science (i.e., object-based programming, etc), the relationships in terms of technical nomenclatures are provided in this glossary section for comparative reference purposes.

Object Identifier (OID): in computing, an identifier used to name an object. An OID, structurally, consists of a node in a hierarchically assigned namespace and is formally defined using Abstract Syntax Notation (i.e., ITU-T ASN.1 standard).

Office Open XML (OOXML): a family of XML schemas, specified in ECMA-376, used for office productivity applications.

Off-Line Editing: any process of selecting the order or composition of content (video, audio, CG) that involves components that are not “on line.” This process is not necessarily nonlinear in nature, as it may involve linear videotape transports and not disk-based digitized media.

On-Line Editing: the process that involved linear postproduction of content using real-time playback of material through video production switchers (also known as “vision mixers”), effects and character generators, and under the control of a computer-assisted edit controller

system that depends on the edit decision list (EDL) generally created during the “off-line” editing process.

Page: the smallest addressable unit for read and program operations.

Performance: a measure of how well a system acts under a prescribed set of circumstances.

Pits: the indentation made when the optical or magneto-optical disc is written to that becomes the instrument for reflecting the laser and thus the method for recording if the data is a logical one or zero.

Platform: a combination of hardware and software assembled to perform specific functions in an environment; it may include the computers, operating systems, servers, storage, human interfaces, etc. Also, the fundamental technology of a system’s hardware and software that defines how a system is operated and determines what other kinds of software or services can be used.

Protocol: a description of rules or digital message formats for the exchange of those messages between communications systems, machines, computing systems, and electronic devices.  Also, a set of syntactical rules that determines behavior of units and their functionality, and specifies the format and relative timing between parties that exchange or communicate information.|

Protocol Data Unit (PDU): the initiator and target divide their communications into messages; the term “iSCSI protocol data unit” (iSCSI PDU) is used for these messages.

RAID Level: the numbering process that describes how an array of disk drives are mathematically arranged for performance or protection of data.

RAID Set: an array of drives configured according to one of the RAID levels.

Real Time: that occurs live or in a continuous unbroken time line.

Real-Time Operating System (RTOS): an operating system that functions in an isochronous (time dependent) mode.

Recovery Time Objective (RTO): a target duration of time taken to return to normal operations in the event of an outage where accessibility to data is lost.

Recovery Point Objective (RPO): the amount of data, measured in time, that you can lose from the outage event (e.g., “we can afford 2 min of downtime before loss of data occurs”).

Redundant Array of Inexpensive Tapes (RAIT): similar in protection features to RAID (Redundant Array of Inexpensive Disks) but modeled with multiple sets of linear data tape drives and tapes; employed as both a protective means and for increased performance or bandwidth.

Replication: the processes of duplicating data to a separate storage system, platform, or location for backup or bandwidth purposes.

Resilient: capable of withstanding shock without permanent deformation or rupture; tending to recover from or adjust easily to misfortune or change.

Resource: in a computer system, any component that can be called upon for a function or a service.

Rotational Latency: the delay in having a disk drive platter to rotate, requiring an additional time in order for the data bits to be positioned precisely below the read head, caused by the head that is not ready to read the data.

Standards CCIR 601 and ITU-R BT.601: the two official names from the standards bodies (CCIR and ITU); and their standards or recommendations nomenclatures for digital video coding. The former (CCIR) is the original name and the latter (ITU) is the current name (International Telecommunication Union-Radiocommunications Sector).

SAN Island: a storage area network (SAN) that stands as a discrete, isolated entity within a larger SAN; which is usually located in a same physical space, a same building, or in a single room.

SATA: acronym for Serial Advanced Technology Attachment.

Scale-Out: also called “horizontal” storage, enables commodity storage components to be combined with multiple small, low cost computers to either (a) create an aggregate storage pool or (b) to increase computing power.

Scale-Up: also known as “vertical” scaling. When a system i.e., servers, workstations, or storage, adds resources (CPUs, memory, etc.,) to a single node in the system.

SCSI: acronym for Small Computer Systems Interface.

SCSI Device: the SCSI architecture model (SAM2) term for an entity that contains one or more SCSI ports that are connected to a service delivery subsystem and supports a SCSI application protocol. For iSCSI, the SCSI Device is the component within an iSCSI Node that provides the SCSI functionality. There can be, at most, one SCSI Device within a given iSCSI Node.

SCSI Parallel Interface (SPI): the physical connectivity (wiring and electrical interface) that supported the carriage of the parallel data sets from host to peripheral devices. SPI was all, but abandoned with the proliferation, of a serial extension of the SCSI suite of protocols.

SCSI Port: the term for an entity in a SCSI Device that provides the SCSI functionality to interface with a service delivery subsystem. Note that for iSCSI, the definition of the SCSI Initiator Port and the SCSI Target Port are different.

Seek Time: the time it takes for the disk drive to go from the previous position to its new position once a data request has been issued.

Session: the group of TCP connections that link an initiator with a target form a channel for communications, known as a session. TCP connections can be added and removed from a session.

Session ID (SSID): a session between an iSCSI initiator and an iSCSI target, explicitly specified by the initiator at session establishment.

Set-Top Box (STB): an electronic device connecting a television display, monitor or receiver and an external signal source, which turns the cable, IP stream, or satellite LNB downconverted signal into a content that is then displayed on a display device.

Set-Top Unit (STU): is alternative name for a set-top box (STB)

Serial Attached SCSI (SAS): a computer bus and its protocols, which move data to and from storage devices including hard disk and data tape drives, over a serial (as opposed to parallel) interface.

Serial Communications: the transmission of data as bits or other formats, which is carried serially, that is, progressively from a transmitter (source) to a receiver (target).

Serial Digital Interface (SDI): in the perspective of video systems, the implementation of a carrier used for the real-time transport of baseband digital video signals for high definition, standard definition, and other packetized data sets.

Serial Storage Architecture (SAS): a peripheral interconnect interface from IBM (and others) developed as an alternative to parallel SCSI which was fault tolerant and consumed less power.

Server: a computer or compute device that may reside on a network or may stand by itself, which manages computer or network centric resources, including storage, applications, and other components.

Shadowing: another name for disk mirroring.

Sharding: term applied to scaling a system to almost infinite proportions by the addition of nodes made from inexpensive computers (used by Google).

Shugart Associates System Interface (SASI): the name given by Shugart, a disk drive, peripheral and component manufacturer that developed what would eventually become SCSI through the standard processes.

Single-Level Cell (SLC): the dominant flash memory technology for SSD in enterprise storage systems.

Single Point of Failure (SPOF): a vulnerability place in a system that, should it cease to operate, has a high risk of forcing a complete failure of that system; the counter to that is NSPOF (no single point of failure).

Small Computer Systems Interface (SCSI): pronounced “scuzzy,” a set of standards for connecting and transferring data between computers and peripheral devices. The SCSI standards define the physical interfaces (connections), the system commands, protocols, and electrical and optical interfaces. The origination of the term came from the “Shugart Associates System Interface” (SASI), developed in the late 1970s.

Sputtering: a coating process that uses a physical vapor deposition (PVD) method for depositing thin films by ejecting material from a source target, which is layered onto a substrate, such as a silicon wafer or the surface of a DVD.

Snapshot: a locally retained point-in-time image of the data presented on a system, which is used in backups or as a reference to what a storage condition looked like should a failure or corruption of a data set occurs.

Snarfing: Information theft or data manipulation in networks. Snarfing, probably portmanteau from the words “snort” and “scarf”, is a cache coherence mechanism.

Storage Density: the measure of the quantity of information that can be stored on a given surface area or in a given physical volume.

Storage Module Device (SMD): an early implementation in the 1970s for connecting storage peripherals.

Storage Tiering: segregating data in tiers (layers) either by hardware, by value, or by virtualization.

Structured Data: data that is organized and referenced.

Superparamagnetism: magnetism that appears in small ferromagnetic or ferrimagnetic nanoparticles.

Switched Bunch of Disks (SBOD): an arrangement of hard disks, which uses an integral crossbar switch to direct traffic to those disks from a single port of a host device.

Symbol: a state or significant condition of the communication channel that persists for a finite period of time.

Symbol Error Rate (SER): the number of symbol errors in a data stream. The symbol rate (also known as baud or modulation rate) is the number of changes made to the transmission medium per second using a digitally modulated signal or a line code.

T10: a technical committee within INCITS that develops standards and technical reports on I/O interfaces, particularly the series of Small Computer Systems Interface (SCSI) standards. See http://www.t10.org.

T11: a technical committee within INCITS responsible for standards development in the areas of Intelligent Peripheral Interface (IPI), High-Performance Parallel Interface (HIPPI), and Fibre Channel (FC). See http://www.t11.org.

Target: the end device which an initiator intends to reach.

Thermally Assisted Recording (TAR): a process that involves temporarily heating an area of the disk to achieve a better signal recovered.

Tiering: layers in a system or a set of components.

Topology: the logical and/or physical arrange of switches and other components of a network; sometimes referred to as the “architecture” of a network.

Transcode: to change the encoding parameters from one form to another, may involve changing the bit rate, profile, level, aspect ratios, and resolution.

Transmission Server: a video server or transport server platform that is configured for long- and short-form playback for delivery of program content over the service (a television broadcaster) or a multiprogram video distributor (cable or satellite broadcaster).

Transrate: to change the data rate from one bit rate to another without necessarily altering the compression (encoding) format.  This process is often utilized by cable MSOs or satellite MVPDs to allow for more program channels to be placed into a cable system or satellite transponder.

Uniform Resource Name (URN): a Uniform Resource Identifier (URI) using the “URN scheme.” Both URNs (names) and URLs (locators) are URIs. A particular URI may be a name and a locator at the same time. Functional Requirements for URNs are described in IETF RFC 1737 (1994). URNs are part of the Internet information architecture composed of URNs (used for identification), URC (Uniform Resource Characteristics for including metainformation), and URL (Uniform Resource Locators for finding or locating resources).

Unstructured Data: data that is random, not interrelated or uncorrelated (such as video or multimedia).

Uptime (availability): ratio of the expected value of the time when a system is operational and committable, as shown below in equation form:

Video Component Signal Sets: the various sets of coded, scaled, and weighted channels in either an analog or a digital representation of a video signal (includes RGB and R'G'B', YUV, Y and Y', G' and C, YPBPR, and Y'PB'PR').

Video Server: a series of components comprised of input and output encoders and decoders, a server platform that manages the flow of data between these devices, and storage aimed at capturing and reproducing moving images, sound, and ancillary data or metadata.

Virtualization: the creation of an implicit (rather than actual) version of something, such as an operating system, a server, a storage device, or a network resource.

Virtual Storage Area Network (VSAN): the allocation of switch ports spanning multiple physical switchers and forms a virtual fabric.

Virtual Systems: any technology that is camouflaged behind an interface that masks the details of how that technology is actually implemented.

Wear Leveling: in flash memory, if the same cells (areas within the memory) are continually

written to, erased, then written to again, the chip will wear out faster. Wear leveling is a preventative measure taken to spread the writing around to various cells to “level” the wearing out more evenly.

Write-Once Read-Many (WORM): the process of writing the data once to a media in such a means that it cannot be altered and may only be “read” in the future (unless the physical media is destroyed).

Wear Out: the degrading effect of successive writes in a NAND Flash memory chip (also called “block wear”).

Wrapper: also called a container, is a specialized metafile describing the grouping of multiple types of audio, video, data, and metadata, which are associated together as a complete “package” that is delivered to a platform.

Write-Back: in a disk cache accelerator process, under heavy disk activities, the cache buffers the write data, holding back requests from being sent to a disk until heavy disk activity is suspended. The cache then writes to the disk during these slower periods (also called copy-back).

XDCAM: Sony’s disc (and flash memory)-based digital recording platform for nonlinear, random access, and file-based workflows.  XDCAM EX is Sony’s solid state media equivalent to the optical disc implementation.

Zoning: the grouping of devices by function or by location.