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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  • O

    object storage

    Object storage, also called object-based storage, is an approach to addressing and manipulating data storage as discrete units, called objects.

  • optical storage

    Optical storage is any storage type in which data is written and read with a laser.

  • orthogonal

    Orthogonal concepts have their roots in advanced mathematics. They are also associated with software development, storage and networking.

  • overprovisioning (SSD overprovisioning)

    Overprovisioning, in a storage context, is the inclusion of extra storage capacity in a solid-state drive.

  • oversubscription

    Oversubscription in a storage area network (SAN) is the practice of committing more network bandwidth to devices connected to that network than what is physically available.

  • What are optical disks and how do they work?

    An optical disk is an electronic data storage medium that can be written to and read from using a low-powered laser beam.

  • P

    parallel file system

    A parallel file system is a software component designed to store data across multiple networked servers.

  • pebibyte (PiB)

    A pebibyte (PiB) is a unit of measure that describes data capacity.

  • persistent storage

    Persistent storage is any data storage device that retains data after power to that device is shut off.

  • petabyte

    A petabyte is a measure of memory or data storage capacity that is equal to 2 to the 50th power of bytes.

  • primary storage (main storage)

    Primary storage is the collective methods and technologies that capture and retain digital information in active use and critical for an organization's operations.

  • program/erase cycle (P/E cycle)

    A solid-state storage program/erase cycle (P/E cycle) is a sequence of events in which data is written to a solid-state NAND flash memory cell, such as the type found in a flash or thumb drive, and is subsequently erased and rewritten.

  • public cloud storage

    Public cloud storage, also called online storage, is a service model that provides data storage on a pay-per-use basis.

  • Pure Storage

    Pure Storage is a provider of enterprise data flash storage products designed to substitute for electromechanical disk arrays.

  • software portability

    Software portability is a characteristic attributed to a computer program if it can run with minimal rework on operating systems (OSes) other than the one for which it was created.

  • What is a partition in computers?

    A partition is a logical division of a hard disk drive (HDD) that's treated as a separate unit by operating systems (OSes) and file systems.

  • What is parity in computing?

    In computers, parity (from the Latin paritas, meaning "equal or equivalent") is a technique that checks whether data has been lost or written over when it is moved from one place in storage to another or when it is transmitted between computers.

  • What is personal cloud storage (PCS)?

    Personal cloud storage (PCS) is a local network-attached storage (NAS) device that lets users store data, photos, music, videos and other files and is optimized for media streaming.

  • Q

    quad-level cell NAND (QLC NAND)

    Quad-level cell NAND (QLC NAND) is a form of NAND flash memory that can store up to 4 bits of data per memory cell.

  • queue depth

    Queue depth, in storage, is the number of pending input/output (I/O) requests that a storage resource can handle at any one time.

  • R

    race condition

    A race condition is an undesirable situation that occurs when a device or system attempts to perform two or more operations at the same time, but because of the nature of the device or system, the operations must be done in the proper sequence to be done correctly.

  • RAID 3 (redundant array of independent disks 3)

    RAID 3 (redundant array of independent disks 3) is a RAID configuration that uses a parity disk to store the information generated by a RAID controller and uses striping to store 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 50 (RAID 5+0)

    RAID 50, also known as RAID 5+0, combines distributed parity (RAID 5) with striping (RAID 0). It requires a minimum of six drives.

  • 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.

  • RAM (random access memory)

    Random access memory (RAM) is the hardware in a computing device that provides temporary storage for the operating system (OS), software programs and any other data in current use so they're quickly available to 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.

  • 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 random access memory)

    RRAM, also known as resistive random access memory or ReRAM, is a form of non-volatile storage that operates by changing the resistance of a specially formulated solid dielectric material.

  • What is RAID (redundant array of independent disks)?

    RAID (redundant array of independent disks) is a way of storing the same data in different places on multiple hard disks or solid-state drives (SSDs) to protect data in the case of a drive failure.

  • What is RAID 0 (disk striping)?

    RAID 0 (disk striping) is the process of dividing a body of data into blocks and spreading the data blocks across multiple storage devices, such as hard disk drives (HDDs) or solid-state drives (SSDs), in a redundant array of independent disks group.

  • What is RAID 5?

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

  • S

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

    A SAS SSD (Serial-Attached SCSI solid-state drive) is a NAND flash memory-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)

    SCSI (Small Computer System Interface) is an electronic interface that enables PCs and servers to communicate with peripheral hardware, such as storage devices, printers and scanners, faster and more flexibly than previous parallel data transfer interfaces.

  • 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.

  • shingled magnetic recording (SMR)

    Shingled magnetic recording (SMR) is a technique for writing data to a hard disk drive (HDD) whereby the data tracks partially overlap to increase the areal density and overall storage capacity per disk.

  • software redundant array of independent disk (software RAID)

    Software RAID, also known as virtual RAID, is a form of RAID (software redundant array of independent disk) performed on an internal server.

  • 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 is a type of computer storage media that stores data electronically and has no moving parts.

  • 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 caching

    SSD caching, also known as 'flash caching' or 'flash memory caching,' is the temporary storage of frequently-accessed data on NAND flash memory chips in a solid-state drive (SSD) to improve the drive's input/output (I/O) performance and allow data requests to be met with improved speed.

  • SSD TRIM

    SSD TRIM is a command for the Advanced Technology Attachment (ATA) interface that enables an operating system (OS) 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 (STaaS) is a managed service in which the provider supplies the customer with access to a data storage platform.

  • 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 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 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 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.

  • What is a storage filer?

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

  • What is 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.

  • What is 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.

  • 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.

  • 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

    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.

  • What is 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 SAS and SATA-based spinning disks and solid-state drives (SSDs).

  • 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 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).

  • 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

    What is 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.

  • Y

    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

    What is a zettabyte (ZB)?

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