Storage Technology Definitions

This glossary explains the meaning of key words and phrases that information technology (IT) and business professionals use when discussing storage and related software products. You can find additional definitions by visiting WhatIs.com or using the search box below.

  • S

    secondary storage

    Secondary storage is persistent storage for noncritical data that doesn't need to be accessed as frequently as data in primary storage or that doesn't have the same performance or availability requirements.

  • sector

    On a computer diskette or hard disk, a sector is one of the "pie slices" the diskette or disk is divided into.

  • Secure Digital card (SD card)

    SD cards use flash memory to provide nonvolatile storage. They are more rugged than traditional storage media and are used in more portable storage media.

  • self-service cloud computing

    Self-service cloud computing is a form of private cloud service where the customer provisions storage and launches applications without going through an external cloud service provider.

  • semiconductor fab

    A semiconductor fab is a manufacturing plant in which raw silicon wafers are turned into integrated circuits. 

  • SerDes (serializer/deserializer)

    A SerDes or serializer/deserializer is an integrated circuit (IC or chip) transceiver that converts parallel data to serial data and vice-versa.

  • Serial ATA (Serial Advanced Technology Attachment or SATA)

    Serial ATA (Serial Advanced Technology Attachment or SATA) is a command and transport protocol that defines how data is transferred between a computer's motherboard and mass storage devices, such as hard disk drives (HDDs), optical drives and solid-state drives (SSDs).

  • Serial-Attached SCSI (SAS)

    Serial-Attached SCSI (SAS) is a method used to access computer peripheral devices that employs a serial -- one bit at a time -- means of digital data transfer over thin cables.

  • server-based SSD

    A server-based SSD is a solid state drive that may be manufactured in a PCI Express form factor.

  • server-based storage

    Server-based storage is a re-emerging class of data storage that removes cost and complexity by housing storage media inside servers rather than in dedicated and custom-engineered storage arrays.

  • shadow RAM

    Shadow RAM is a copy of Basic Input/Output Operating System (BIOS) routines from read-only memory (ROM) into a special area of random access memory (RAM) so that they can be accessed more quickly.

  • shingled magnetic recording (SMR)

    Shingled magnetic recording (SMR) is a technique for writing data to disk drives in partially overlapping tracks to boost areal density and overall capacity.

  • short stroking

    Short stroking is the practice of formatting a disk drive such that data is written only to the outer sectors of the disk's platters.

  • Single namespace

    A single namespace is one presentation of file system data.

  • single-level cell (SLC) flash

    Single-level cell (SLC) flash is a type of solid-state storage that stores one bit of data per cell of flash media.

  • soft zoning

    Soft zoning is used to allocate resources and control access in a storage-area network (SAN).

  • software RAID (software redundant array of independent disk)

    Software RAID is a form of RAID (redundant array of independent disks) performed on the internal server.

  • software-defined storage (SDS)

    Software-defined storage (SDS) is a computer program that manages data storage resources and functionality and has no dependencies on the underlying physical storage hardware.

  • solid state module (SSM)

    A solid state module is solid state storage that resides in a Dual In-line Memory Module (DIMM) or similar form factor. 

  • solid-state drive (SSD) capacity

    Solid-state drive (SSD) capacity is the maximum amount of data that can be stored on a solid-state drive.

  • solid-state storage

    Solid-state storage (SSS) is a type of computer storage media made from silicon microchips. SSS stores data electronically instead of magnetically, as spinning hard disk drives (HDDs) or magnetic oxide tape do.

  • solid-state storage garbage collection

    Solid-state storage garbage collection, or SSD garbage collection, is an automated process by which a solid-state drive (SSD) improves write performance.

  • solid-state storage UBER

    Solid-state storage UBER (unrecoverable bit error rate) is the percentage of bits that have errors relative to the total number of bits that have been read.

  • spindle

    A spindle is a shaft that holds rotating hard disk drive (HDD) platters in place. The term is also often used to refer to a single HDD.

  • SSD (solid-state drive)

    An SSD, or solid-state drive, is a type of storage device used in computers.

  • SSD caching

    SSD caching, also known as flash caching, is the temporary storage of data on NAND flash memory chips in a solid-state drive so data requests can be met with improved speed.

  • SSD form factor

    An SSD form factor is the size, configuration or physical arrangement of solid state storage media. The form factor determines the media's physical compatibility and interchangeability with other computer components or devices.

  • SSD purge (solid state drive purge)

    SSD purge is the process of returning a flash memory device to its original state at the time of manufacturing and effectively erasing any data that has been written to the device. A purge is sometimes called a hard reset or digital sanitization. 

  • SSD RAID (solid-state drive RAID)

    SSD RAID (solid-state drive RAID) is a methodology commonly used to protect data by distributing redundant data blocks across multiple SSDs.

  • SSD TRIM

    SSD TRIM is an Advanced Technology Attachment (ATA) command that enables an operating system to inform a NAND flash solid-state drive (SSD) which data blocks it can erase because they are no longer in use.

  • SSD write cycle

    An SSD write cycle is the process of programming data to a NAND flash memory chip in a solid-state storage device.

  • stand-alone solid state storage (SSS)

    Stand-alone SSS is solid state storage that is not integrated with spinning hard drive disks as in a hybrid flash array.

  • Standard MIDI File (SMF)

    The SMF (Standard MIDI File) was developed to allow musicians and audio file developers to transfer their sequenced MIDI data from one software application to another.

  • steady state

    Steady state is a condition in which a solid state flash drive has experienced enough program/erase (P/E) cycles that performance times for write operations becomes stable and can be evaluated in a consistent manner.

  • storage (computer storage)

    Data storage is the collective methods and technologies that capture and retain digital information on electromagnetic, optical or silicon-based storage media.

  • storage as a service (STaaS)

    Storage as a service can be delivered on premises from infrastructure that is dedicated to a single customer, or it can be delivered from the public cloud as a shared service that's purchased by subscription and is billed according to one or more usage metrics.

  • storage at the edge

    Storage at the edge is the collective methods and technologies that capture and retain digital information at the periphery of the network, as close to the originating source as possible.

  • storage capacity planning

    Storage capacity planning is the practice of assessing current data storage needs and forecasting future storage requirements.

  • storage class memory (SCM)

    Storage class memory (SCM) is a type of physical computer memory that combines dynamic random access memory (DRAM), NAND flash memory and a power source for data persistence.

  • storage consolidation

    Storage consolidation, also called storage convergence is a method of centralizing data storage among multiple servers.

  • storage encryption

    Storage encryption is the use of encryption/decryption of backed-up and archived data, both in transit and on storage media.

  • storage filer

    A storage filer is a type of file server designed and programmed for high-volume data storage, backup and archiving.

  • storage hypervisor

    Storage hypervisors make more efficient use of storage resources in a virtual environment.

  • storage medium (storage media)

    In computers, a storage medium is a physical device that receives and retains electronic data for applications and users and makes the data available for retrieval.

  • storage node

    A storage node is typically a physical server with one or more hard-disk drives (HDDs) or solid-state drives (SDDs).

  • storage provisioning

    Storage provisioning is the process of assigning storage, usually in the form of server disk drive space, in order to optimize the performance of a storage area network (SAN)...(Continued)

  • storage security

    Storage security is the group of parameters and settings that make storage resources available to authorized users and trusted networks -- and unavailable to other entities.

  • storage stack

    A storage stack, also called an integrated stack, is a bundled storage product that include servers, networking components and server virtualization software. 

  • storage utilization

    Storage utilization is a measure of how well the available data storage space in an enterprise is used.

  • storage virtualization

    Storage virtualization is the pooling of physical storage from multiple storage devices into what appears to be a single storage device -- or pool of available storage capacity -- that is managed from a central console.

  • storage volume

    A storage volume is an identifiable unit of data storage. It can be a removable hard disk, but it does not have to be a unit that can be physically removed from a computer or storage system.

  • switching fabric

    Switching fabric is the combination of hardware and software that moves data coming in to a network node out by the correct port (door) to the next node in the network.

  • synchronous mirroring

    Synchronous mirroring is a type of data protection in which data is written to both a remote and local disk simultaneously.

  • What is a SAN? Ultimate storage area network guide

    A storage area network (SAN) is a dedicated high-speed network or subnetwork that interconnects and presents shared pools of storage devices to multiple servers.

  • T

    tape drive

    A tape drive is a device that stores computer data on magnetic tape, especially for backup and archiving purposes.

  • tebibyte (TiB)

    A tebibyte (TiB) is a unit of measure used to describe computing capacity.

  • Terabyte (TB)

    A terabyte (TB) is a unit of digital data that is equal to about 1 trillion bytes.

  • thick provisioning

    Thick provisioning pre-allocates storage capacity on a disk rather than on an as-needed basis.

  • thin provisioning (TP)

    Thin provisioning (TP) is a method of optimizing the efficiency with which the available space is utilized in storage area networks... (Continued)

  • thin server

    In the computer industry, a thin server is a PC that contains just enough hardware and software to support a particular function that users can share in a network, such as access to files on a storage device, access to CD-ROM drives, printing, or Internet access.

  • Tier 0

    Tier 0 (tier zero) is a level of data storage that is faster, and perhaps more expensive, than any other level in the storage hierarchy.

  • Tier 1 storage

    Tier 1 storage is a reference to the higher performing systems in a tiered storage environment.

  • tiered storage

    Tiered storage is a method for assigning different categories of data to various types of storage media to reduce overall storage costs and improve the performance and availability of mission-critical applications.

  • TLC flash (triple-level cell flash)

    TLC flash (triple-level cell flash) is a type of NAND flash memory that stores three bits of data per cell.

  • tunnel injection

    Tunnel injection, also called Fowler-Nordheim tunnel injection, is the process by which data is written to NAND flash memory.  

  • two-spindle system (twin-spindle system)

    A two-spindle system, also called a twin-spindle system, is a computer design with two internal storage drives.

  • U

    U.2 SSD (formerly SFF-8639)

    A U.2 SSD is a high-performance data storage device designed to support the Peripheral Component Interconnect Express (PCIe) interface using a small form factor (SFF) connector that is also compatible with standard Serial-Attached SCSI (SAS) and Serial Advanced Technology Attachment (SATA)-based spinning disks and solid-state drives (SSDs).

  • Ultra DMA (UDMA or Ultra DMA/33)

    Ultra DMA (UDMA, or, more accurately, Ultra DMA/33) is a protocol for transferring data between a hard disk drive through the computer's data paths (or bus) to the computer's random access memory (RAM).

  • unified storage (multiprotocol storage)

    Unified storage -- sometimes called network unified storage or multiprotocol storage -- is a storage system that makes it possible to run and manage files and applications from a single device.

  • USB flash drive

    A USB flash drive -- also known as a stick, thumb or pen drive -- is a plug-and-play portable storage device that uses flash memory and can attach to a keychain.

  • utility storage

    Utility storage is a service model in which a provider makes storage capacity available to an individual, organization or business unit on a pay-per-use basis.

  • V

    VCD (video CD or video compact disc)

    VCD (also called video CD, video compact disc or "disc") is a compact diskformat based on CD-ROM XAthat is specifically designed to hold MPEG-1video data and to include interactive capabilities.

  • virtual LUN (virtual logical unit number)

    A virtual LUN (virtual logical unit number) is a representation of a storage area that is not tied to any physical storage allocation.

  • virtual memory

    Virtual memory is a memory management technique where secondary memory can be used as if it were a part of the main memory.

  • virtual provisioning

    Virtual provisioning is a term used by vendors, such as EMC, to describe a process of efficiently provisioning space in storage area networks (SAN). (Continued...)

  • virtual SAN appliance (VSA)

    A virtual SAN appliance (VSA) is a software bundle that allows a storage manager to turn the unused storage capacity in his network's virtual servers into a storage area network (SAN).

  • virtual storage area network (VSAN)

    A virtual storage area network (VSAN) is a logical partition in a physical storage area network (SAN).

  • virtual tape

    Virtual tape is an archival storage technology that makes it possible to save data as if it were being stored on tape although it may actually be stored on hard disk or on another storage medium.

  • VMware Storage Policy-Based Management

    Storage Policy-Based Management is a feature that allows for automatic provisioning of virtual machines in a VMware environment.

  • volume manager

    A volume manager is software within an operating system (OS) that controls capacity allocation for storage arrays.

  • VRAM (video RAM)

    VRAM (video RAM) refers to any type of random access memory (RAM) specifically used to store image data for a computer display.

  • W

    wear leveling

    Wear leveling is a process that is designed to extend the life of solid-state storage devices.

  • Windows Storage Server 2012

    Microsoft Windows Storage Server 2012 (WSS 2012) is a platform for network-attached storage (NAS ) appliances and iSCSI storage systems.

  • Windows Storage Spaces

    Windows Storage Spaces is a feature in Microsoft Windows Server 2012 that is used to virtualize and provision storage.

  • World Wide Name (WWN)

    A World Wide Name (WWN) is a unique identifier that is hard-coded into each Fibre Channel (FC) device by the device's manufacturer.

  • WORM (write once, read many)

    In computer media, write once, read many, or WORM, is a data storage technology that allows data to be written to a storage medium a single time and prevents the data from being erased or modified.

  • WRAM (Window RAM)

    Window RAM (WRAM), unrelated to Microsoft Windows, is very high-performance video RAM that is dual-ported and has about 25% more bandwidth than VRAM but costs less.

  • write amplification

    Write amplification is an issue that occurs in solid state storage devices that can decrease the lifespan of the device and impact performance.

  • write amplification factor (WAF)

    Write amplification factor (WAF) is a numerical value that represents the amount of data a solid-state drive (SSD) controller writes in relation to the amount of data that the host's flash controller writes.

  • write endurance

    Write endurance is the number of program/erase (P/E) cycles that can be applied to a block of flash memory before the storage media becomes unreliable.

  • X

    XAM (eXtensible Access Method)

    XAM (eXtensible Access Method) is a standard that makes it easier to manage fixed content by freeing data from dependencies on location, applications and storage devices.

  • XFS file system

    XFS is a 64-bit, highly scalable file system that was developed by Silicon Graphics Inc. (SGI) and first deployed in the Unix-based IRIX operating system (OS) in 1994.

  • Y

    yobibyte (YiB)

    A yobibyte (YiB) is a unit of measure used to describe data capacity as part of the binary system of measuring computing and storage capacity.

  • yottabyte (YB)

    A yottabyte (YB) is a measure of theoretical storage capacity and data volumes equal to 2 to the 80th power bytes, or approximately a million trillion megabytes (MB).

  • Z

    Zadara VPSA and ZIOS

    Zadara Storage provides block, file or object storage with varying levels of compute and capacity through its ZIOS and VPSA platforms.

  • zebibyte (ZiB)

    A zebibyte (ZiB) is a unit used to measure computing and storage capacity.

  • zettabyte

    A zettabyte is a unit of measurement used by technology professionals and the general public to describe a computer or other device's storage capacity.

  • ZFS

    ZFS is a local file system and logical volume manager created by Sun Microsystems to control the placement, storage and retrieval of data in enterprise computing systems.

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