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.

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  • R

    RAID 10 (RAID 1+0)

    RAID 10, also known as RAID 1+0, is a RAID configuration that combines disk mirroring and disk striping to protect data.

  • RAID 3 (redundant array of independent disks)

    RAID 3 is a RAID configuration that uses striping and parity, but it uses a parity disk to store the parity information generated by a RAID controller instead of striping it with the data.

  • RAID 4 (redundant array of independent disks)

    RAID 4 (redundant array of independent disks) is a RAID configuration that uses a dedicated parity disk and block-level striping across multiple disks.

  • RAID 5

    RAID 5 is a redundant array of independent disks configuration that uses disk striping with parity.

  • RAID 50 (RAID 5+0)

    RAID 50, also known as RAID 5+0, combines distributed parity (RAID 5) with striping (RAID 0).

  • RAID 6

    RAID 6, also known as double-parity RAID, is one of several RAID schemes that work by placing data on multiple disks and enabling I/O operations to overlap in a balanced way, improving performance.

  • RAID controller

    A RAID controller is a hardware device or software program used to manage hard disk drives or solid-state drives in a computer or storage array so they work as a logical unit.

  • RAM (Random Access Memory)

    RAM (Random Access Memory) is the hardware in a computing device where the operating system (OS), application programs and data in current use are kept so they can be quickly reached by the device's processor.

  • RAM-based solid-state drive (SSD)

    A RAM-based solid-state drive (SSD) is a storage device made from silicon microchips that has no moving parts and stores data electronically instead of magnetically.

  • RDRAM (Rambus DRAM)

    Rambus Dynamic Random Access Memory, or RDRAM (Rambus DRAM), is a type of computer device active memory developed and licensed by Rambus Inc.

  • read-intensive SSD (read-intensive solid-state drive)

    A read-intensive solid-state drive (SSD) is a NAND flash-based storage or caching device used with applications that write data infrequently, in contrast to SSDs that target write-intensive workloads.

  • Red Hat OpenStack Platform

    Red Hat OpenStack Platform is a commercially supported distribution of open source OpenStack software designed to build and manage large pools of compute, storage and networking resources in public and private clouds.

  • redundant

    Data redundancy refers to the practice of keeping data in two or more places within a database or data storage system.

  • Remote Direct Memory Access (RDMA)

    Remote Direct Memory Access (RDMA) is a technology that enables two networked computers to exchange data in main memory without relying on the processor, cache or operating system of either computer.

  • RRAM or ReRAM (resistive RAM)

    RRAM or ReRAM (resistive random access memory) is a form of nonvolatile storage that operates by changing the resistance of a specially formulated solid dielectric material.

  • S

    SAN switch (storage area network switch)

    A SAN switch (storage area network switch) is a device that connects servers and shared pools of storage devices and is dedicated to moving storage traffic.

  • SAS SSD (Serial-Attached SCSI solid-state drive)

    A SAS SSD (Serial-Attached SCSI solid-state drive) is a NAND flash-based storage or caching device designed to fit in the same slot as a hard disk drive (HDD) and use the SAS interface to connect to the host computer.

  • SATA Express (SATAe)

    SATA Express (SATAe or Serial ATA Express) is a bus interface to connect storage devices to a computer motherboard, supporting SATA and PCI Express protocols simultaneously.

  • SCSI (Small Computer System Interface)

    Definition: The Small Computer System Interface (SCSI) is a set of parallel interface standards used to attach disk drives and other peripherals to a computer.

  • 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.

  • 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.

  • semiconductor fab

    A semiconductor fab -- short for fabrication -- is a manufacturing plant in which raw silicon wafers are turned into integrated circuits (ICs).

  • 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 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.

  • 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.

  • 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.

  • 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 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.

  • 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 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.

  • 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 filer

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

  • 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 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 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.

  • 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.

  • 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.

  • Tier 0

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

  • 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.

  • 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).

  • 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

    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 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).

  • 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.

  • 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.

  • 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.

  • 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

    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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