Computer data storage - Wikipedia

Computer data storage - Wikipedia
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Storage of digital data readable by computers
For broader coverage of this topic, see
Data storage
GiB
of
SDRAM
mounted in a
computer
. An example of
primary storage
15
GB
PATA
hard disk drive (HDD) from 1999. When connected to a computer it serves as
secondary
storage.
Computer memory
and
data storage
types
General
Memory cell
Memory coherence
Cache coherence
Memory hierarchy
Memory access pattern
Memory map
Secondary storage
MOS memory
floating-gate
Continuous availability
Areal density (computer storage)
Block (data storage)
Object storage
Direct-attached storage
Network-attached storage
Storage area network
Block-level storage
Single-instance storage
Data
Structured data
Unstructured data
Big data
Metadata
Data compression
Data corruption
Data cleansing
Data degradation
Data integrity
Data security
Data validation
Data validation and reconciliation
Data recovery
Storage
Data cluster
Directory
Shared resource
File sharing
File system
Clustered file system
Distributed file system
Distributed file system for cloud
Distributed data store
Distributed database
Database
Data bank
Data storage
Data store
Data deduplication
Data structure
Data redundancy
Replication (computing)
Memory refresh
Storage record
Information repository
Knowledge base
Computer file
Object file
File deletion
File copying
Backup
Core dump
Hex dump
Data communication
Information transfer
Temporary file
Copy protection
Digital rights management
Volume (computing)
Boot sector
Master boot record
Volume boot record
GUID Partition Table
Disk array
Disk image
Disk mirroring
Disk aggregation
Disk partitioning
Memory segmentation
Locality of reference
Logical disk
Storage virtualization
Virtual memory
Memory-mapped file
Software entropy
Software rot
In-memory database
In-memory processing
Persistence (computer science)
Persistent data structure
RAID
Non-RAID drive architectures
Memory paging
Bank switching
Grid computing
Cloud computing
Cloud storage
Fog computing
Edge computing
Dew computing
The law
Martiels law
Volatile
RAM
Hardware cache
CPU cache
Scratchpad memory
DRAM
eDRAM
SDRAM
SGRAM
DDR
GDDR
LPDDR
QDRSRAM
EDO DRAM
XDR DRAM
RDRAM
HBM
SRAM
1T-SRAM
ReRAM
QRAM
Content-addressable memory
(CAM)
Computational RAM
VRAM
Dual-ported RAM
Video RAM (dual-ported DRAM)
Historical
DC3MWCP
(1946–1947)
Delay-line memory
(1947)
Mellon optical memory
(1951)
Selectron tube
(1952)
Dekatron
T-RAM
(2009)
Z-RAM
(2002–2010)
Non-volatile
ROM
Diode matrix
MROM
PROM
EPROM
EEPROM
ROM cartridge
Solid-state storage
(SSS)
Flash memory
is used in:
Solid-state drive
(SSD)
Solid-state hybrid drive
(SSHD)
USB flash drive
IBM FlashSystem
Flash Core Module
Memory card
Memory Stick
CompactFlash
PC Card
MultiMediaCard
SD card
SIM card
SmartMedia
Universal Flash Storage
SxS
MicroP2
XQD card
Programmable metallization cell
NVRAM
Memistor
Memristor
PCM
3D XPoint
MRAM
Electrochemical RAM
(ECRAM)
Nano-RAM
CBRAM
Early-stage
NVRAM
FeRAM
ReRAM
FeFET memory
Analog recording
Phonograph cylinder
Phonograph record
Quadruplex videotape
Vision Electronic Recording Apparatus
Magnetic recording
Magnetic storage
Magnetic tape
Magnetic-tape data storage
Tape drive
Tape library
Digital Data Storage
(DDS)
Videotape
Cassette tape
Linear Tape-Open
Betamax
8 mm video format
DV
MiniDV
MicroMV
U-matic
VHS
S-VHS
VHS-C
D-VHS
Hard disk drive
Optical
3D optical data storage
Optical disc
LaserDisc
Compact Disc Digital Audio
(CDDA)
CD
CD Video
CD-R
CD-RW
Video CD
Super Video CD
Mini CD
Nintendo optical discs
CD-ROM
Hyper CD-ROM
DVD
DVD+R
DVD-Video
DVD card
DVD-RAM
MiniDVD
HD DVD
Blu-ray
Ultra HD Blu-ray
Holographic Versatile Disc
WORM
In development
CBRAM
Racetrack memory
NRAM
Millipede memory
ECRAM
Patterned media
Holographic data storage
Electronic quantum holography
5D optical data storage
DNA digital data storage
Universal memory
Time crystal
Quantum memory
UltraRAM
Historical
Paper data storage
(1725)
Punched card
(1725)
Punched tape
(1725)
Plugboard
Drum memory
(1932)
Magnetic-core memory
(1949)
Plated-wire memory
(1957)
Core rope memory
(1960s)
Thin-film memory
(1962)
Disk pack
(1962)
Twistor memory
(~1968)
Bubble memory
(~1970)
Floppy disk
(1971)
Computer data storage
or
digital data storage
is the retention of
digital data
via
technology
consisting of
computer
components and
recording media
. Digital data storage is a core function and fundamental component of computers.
: 15–16
Generally, the faster and volatile storage components are referred to as "
memory
", while slower persistent components are referred to as "storage". This distinction was extended in the
Von Neumann architecture
, where the
central processing unit
(CPU) consists of two main parts: The
control unit
and the
arithmetic logic unit
(ALU). The former controls the flow of data between the CPU and memory, while the latter performs arithmetic and
logical operations
on data. In practice, almost all computers use a
memory hierarchy
: 468–473
which puts memory close to the CPU and storage further away.
In modern computers,
hard disk drives
(HDDs) or
solid-state drives
(SSDs) are usually used as storage.
Data
edit
A modern
digital computer
represents
data
using the
binary numeral system
. The
memory cell
is the fundamental building block of
computer memory
, storing stores one bit of binary information that can be set to store a 1, reset to store a 0, and accessed by reading the cell.
Text, numbers, pictures, audio, and nearly any other form of information can be converted into a string of
bits
, or binary digits, each of which has a value of 0 or 1. The most common unit of storage is the
byte
, equal to 8 bits.
Digital data
comprises the binary representation of a piece of information, often being
encoded
by assigning a bit pattern to each
character
digit
, or
multimedia
object. Many standards exist for encoding (e.g.
character encodings
like
ASCII
, image encodings like
JPEG
, and video encodings like
MPEG-4
).
Encryption
edit
For
security reasons
, certain types of data may be
encrypted
in storage to prevent the possibility of unauthorized information reconstruction from chunks of storage snapshots. Encryption in transit protects data as it is being transmitted.
Compression
edit
Data compression
methods allow in many cases (such as a database) to represent a string of bits by a shorter bit string ("compress") and reconstruct the original string ("decompress") when needed. This utilizes substantially less storage (tens of percent) for many types of data at the cost of more computation (compress and decompress when needed). Analysis of the trade-off between storage cost saving and costs of related computations and possible delays in data availability is done before deciding whether to keep certain data compressed or not.
Vulnerability and reliability
edit
Distinct types of data storage have different points of failure and various methods of
predictive failure analysis
. Vulnerabilities that can instantly lead to total loss are
head crashing
on mechanical hard drives and
failure of electronic components
on flash storage.
Redundancy
edit
Redundancy
allows the computer to detect errors in coded data (for example, a random
bit flip
due to random
radiation
) and correct them based on mathematical algorithms. The
cyclic redundancy check
(CRC) method is typically used in communications and storage for
error detection
. Redundancy solutions include
storage replication
disk mirroring
and RAID (
Redundant Array of Independent Disks
).
Error detection
edit
Error rate measurement
on a
DVD+R
. The minor errors are correctable and within a healthy range.
Impending failure on
hard disk drives
is estimable using
S.M.A.R.T.
diagnostic data that includes the
hours of operation
and the count of spin-ups, though its reliability is disputed.
The health of
optical media
can be determined by
measuring correctable minor errors
, of which high counts signify deteriorating and/or low-quality media. Too many consecutive minor errors can lead to data corruption. Not all vendors and models of
optical drives
support error scanning.
Architecture
edit
Without a significant amount of memory, a computer would only be able to perform fixed operations and immediately output the result, thus requiring hardware
reconfiguration
for a new program to be run. This is often used in devices such as desk
calculators
digital signal processors
, and other specialized devices.
Von Neumann machines
differ in having a memory in which operating
instructions
and data are stored,
: 20
such that they do not need to have their hardware reconfigured for each new program, but can simply be
reprogrammed
with new in-memory instructions. They also tend to be simpler to
design
, in that a relatively simple
processor
may keep
state
between successive computations to build up complex procedural results. Most modern computers are von Neumann machines.
Storage and memory
edit
In contemporary usage, the term "storage" typically refers to a subset of computer data storage that comprises storage devices and their media not directly accessible by the
CPU
, that is,
secondary
or
tertiary storage
. Common forms of storage include
hard disk drives
optical disc
drives, and
non-volatile
devices (i.e. devices that retain their contents when the computer is powered down).
On the other hand, the term "
memory
" is used to refer to
semiconductor
read-write
data storage, typically
dynamic random-access memory
(DRAM).
Dynamic random-access memory
is a form of volatile memory that also requires the stored information to be periodically reread and rewritten, or
refreshed
static RAM
(SRAM) is similar to DRAM, albeit it never needs to be refreshed as long as power is applied.
In contemporary usage, the
memory hierarchy
of primary storage and secondary storage in some uses refer to what was historically called, respectively,
secondary storage
and
tertiary storage
Primary
edit
Various forms of storage, divided according to their distance from the
central processing unit
. The fundamental components of a general-purpose computer are
arithmetic and logic unit
control circuitry
, storage space, and
input/output
devices. Technology and capacity as in common
home computers
around 2005.
Main memory
(also known as
primary memory
internal memory
or
primary storage
), often referred to simply as
memory
, is storage directly accessible to the CPU. The CPU continuously reads instructions stored there and executes them as required. Any data actively operated on is also stored there in a uniform manner. Historically,
early computers
used
delay lines
Williams tubes
, or rotating
magnetic drums
as primary storage. By 1954, those unreliable methods were mostly replaced by
magnetic-core memory
. Core memory remained dominant until the 1970s, when advances in
integrated circuit
technology allowed
semiconductor memory
to become economically competitive.
This led to modern
random-access memory
, which is small-sized, light, and relatively expensive. RAM used for primary storage is
volatile
, meaning that it loses the information when not powered for a specific
time
. Besides storing opened programs, it serves as
disk cache
and
write buffer
to improve both reading and writing performance. Operating systems borrow RAM capacity for caching so long as it's not needed by running software.
Spare memory can be utilized as
RAM drive
for temporary high-speed data storage. Besides main large-capacity RAM, there are two more sub-layers of primary storage:
Processor registers
are the fastest of all forms of data storage, being located inside the processor, with each register typically holding a
word
of data (often 32 or 64 bits). CPU instructions instruct the
arithmetic logic unit
to perform various calculations or other operations on this data.
Processor cache
is an intermediate stage between faster registers and slower main memory, being faster than main memory but with much less capacity. Multi-level
hierarchical cache
setup is also commonly used, such that primary cache is the smallest and fastest, while secondary cache is larger and slower.
Primary storage, including
ROM
EEPROM
NOR flash
, and
RAM
10
is usually
byte-addressable
. Such memory is directly or indirectly connected to the central processing unit via a
memory bus
, comprising an
address bus
and a
data bus
. The CPU firstly sends a number called the
memory address
through the address bus that indicates the desired location of data. Then it reads or writes the data in the
memory cells
using the data bus. Additionally, a
memory management unit
(MMU) is a small device between CPU and RAM recalculating the actual memory address. Memory management units allow for
memory management
; they may, for example, provide an
abstraction
of
virtual memory
or other tasks.
BIOS
edit
Non-volatile primary storage
containing a small startup program (
BIOS
) is used to
bootstrap
the computer, that is, to read a larger program from non-volatile secondary storage to RAM and start to execute it. A non-volatile technology used for this purpose is called
read-only memory
(ROM). Most types of "ROM" are not literally read only but are difficult and slow to write to
Some
embedded systems
run programs directly from ROM, because such programs are rarely changed. Standard computers largely do not store many programs in ROM, apart from
firmware
, and use large capacities of secondary storage.
Secondary
edit
Secondary storage
(also known as
external memory
or
auxiliary storage
) differs from primary storage in that it is not directly accessible by the CPU. Computers use
input/output
channels to access secondary storage and transfer the desired data to primary storage. Secondary storage is non-volatile, retaining data when its power is shut off. Modern computer systems typically have two orders of magnitude more secondary storage than primary storage because secondary storage is less expensive.
In modern computers,
hard disk drives
(HDDs) or
solid-state drives
(SSDs) are usually used as secondary storage. The
access time
per byte for HDDs or SSDs is typically measured in
milliseconds
, while the access time per byte for primary storage is measured in
nanoseconds
. Rotating
optical storage
devices, such as
CD
and
DVD
drives, have even longer access times. Other examples of secondary storage technologies include
USB flash drives
floppy disks
magnetic tape
paper tape
punched cards
, and
RAM disks
To reduce the seek time and rotational latency, secondary storage, including
HDD
ODD
and
SSD
, are transferred to and from
disks
in large contiguous blocks. Secondary storage is
addressable
by block; once the
disk read/write head
on HDDs reaches the proper placement and the data, subsequent data on the track are very fast to access. Another way to reduce the I/O bottleneck is to use multiple disks in parallel to increase the bandwidth between primary and secondary memory, for example, using
RAID
11
Secondary storage is often formatted according to a
file system
format, which provides the abstraction necessary to organize data into
files
and
directories
, while also providing
metadata
describing the owner of a certain file, the access time, the access permissions, and other information. Most computer
operating systems
use the concept of
virtual memory
, allowing the utilization of more primary storage capacity than is physically available in the system. As the primary memory fills up, the system moves the least-used chunks (
pages
) to a swap file or page file on secondary storage, retrieving them later when needed.
Tertiary
edit
A large
tape library
, with tape cartridges placed on shelves in the front, and a robotic arm moving in the back. The visible height of the library is about 180 cm.
Tertiary storage
or
tertiary memory
typically involves a
robotic arm
which mounts and dismount removable mass storage media from a catalog
database
into a storage device according to the system's demands. It is primarily used for archiving rarely accessed information, since it is much slower than secondary storage (e.g. 5–60 seconds vs. 1–10 milliseconds). This is primarily useful for extraordinarily large data stores, accessed without human operators. Typical examples include
tape libraries
optical jukeboxes
, and massive arrays of idle disks (
MAID
). Tertiary storage is also known as
nearline storage
because it is "near to online".
12
Hierarchical storage management
is an archiving strategy involving automatically migrating long-unused files from fast hard disk storage to libraries or jukeboxes.
Offline
edit
Offline storage
is computer data storage on a medium or a device that is not under the control of a
processing unit
13
The medium is recorded, usually in a secondary or tertiary storage device, and then physically removed or disconnected. Unlike tertiary storage, it cannot be accessed without human interaction. It is used to
transfer information
since the detached medium can easily be physically transported. In modern personal computers, most secondary and tertiary storage media are also used for offline storage.
Network connectivity
edit
A secondary or tertiary storage may connect to a computer utilizing
computer networks
. This concept does not pertain to the primary storage.
Direct-attached storage
(DAS) is a traditional mass storage, that does not use any network.
Network-attached storage
(NAS) is mass storage attached to a computer which another computer can access at file level over a
local area network
, a private
wide area network
, or in the case of
online file storage
, over the
Internet
. NAS is commonly associated with the
NFS
and
CIFS/SMB
protocols.
Storage area network
(SAN) is a specialized network, that provides other computers with storage capacity. SAN is commonly associated with
Fibre Channel
networks.
Cloud
edit
Cloud storage
is based on highly
virtualized
infrastructure.
14
A subset of
cloud computing
, it has particular cloud-native interfaces, near-instant elasticity and
scalability
multi-tenancy
, and
metered
resources. Cloud storage services can be used from an off-premises service or deployed on-premises.
15
Deployment models
edit
Cloud deployment models define the interactions between cloud providers and customers.
16
Private clouds
, for example, are used in
cloud security
to mitigate the increased
attack surface area
of
outsourcing
data storage.
17
A private cloud is cloud infrastructure operated solely for a single organization, whether managed internally or by a third party, or hosted internally or externally.
18
Hybrid cloud storage
are another cloud security solution, involving storage infrastructure that uses a combination of on-premises storage resources with cloud storage. The on-premises storage is usually managed by the organization, while the public cloud storage provider is responsible for the management and security of the data stored in the cloud.
19
20
Using a hybrid model allows data to be ingested in an encrypted format where the key is held within the on-premise infrastructure and can limit access to the use of on-premise
cloud storage gateways
, which may have options to encrypt the data prior to transfer.
21
Cloud services are considered "public" when they are delivered over the public Internet.
22
virtual private cloud
(VPC) is a pool of shared resources within a public cloud that provides a certain level of isolation between the different users using the resources. VPCs achieve user isolation through the allocation of a private IP
subnet
and a virtual communication construct (such as a
VLAN
or a set of
encrypted communication
channels) between users as well as the use of a
virtual private network
(VPN) per VPC user, securing, by means of authentication and encryption, the remote access of the organization to its VPC resources.
citation needed
Types
edit
There are three types of cloud storage:
Object storage
23
24
File storage
Block-level storage
is a concept in cloud-hosted
data persistence
where
cloud services
emulate the behaviour of a traditional
block device
, such as a physical
hard drive
25
where storage is organised as
blocks
. Block-level storage differs from
object stores
or 'bucket stores' or to
cloud databases
. These operate at a higher level of abstraction and are able to work with entities such as files, documents, images, videos or database records.
26
At one time, block-level storage was provided by
SAN
, and NAS provided file-level storage.
27
With the shift from on-premises hosting to cloud services, this distinction has shifted.
28
Instance stores are a form of cloud-hosted block-level storage, being provided as part of a cloud
instance
29
Unlike other forms of block storage, instance store data will be lost the cloud instance is stopped.
30
Characteristics
edit
A 1 GiB module of
laptop
DDR2
RAM
Storage technologies at all levels of the storage hierarchy can be differentiated by evaluating certain core characteristics as well as measuring characteristics specific to a particular implementation. These core characteristics are:
Volatility
An
uninterruptible power supply
(UPS) can be used to give a computer a brief window of time to move information from primary volatile storage into non-volatile storage before the batteries are exhausted. Some systems, for example
EMC Symmetrix
, have integrated batteries that maintain volatile storage for several minutes.
Mutability
Storage can be classified into read/write, slow-write/fast-read (e.g.
CD-RW
SSD
),
write-once/read-many
or WORM (e.g.
programmable read-only memory
CD-R
), read-only storage (e.g.
mask ROM ICs
CD-ROM
).
Types of access include
random access
and
sequential access
. In random access, any location in storage can be accessed at any moment in approximately the same amount of time. In sequential access, the accessing of pieces of information will be in a serial order, one after the other; therefore the time to access a particular piece of information depends upon which piece of information was last accessed.
Addressability
Storage can be location accessible (i.e. selected with its numerical
memory address
),
file addressable
, or
content-addressable
Capacity and
density
Performance
Storage performance metrics include
latency
throughput
, granularity and reliability.
Energy
Low capacity
solid-state drives
have no moving parts and consume less power than hard disks.
31
32
33
Also, memory may use more power than hard disks.
33
Large caches, which are used to avoid hitting the
memory wall
, may also consume a large amount of power.
Security
34
Overview
Characteristic
Hard disk drive
Optical disc
Flash memory
Random-access memory
Linear tape-open
Technology
Magnetic disk
Laser
beam
Semiconductor
Magnetic tape
Volatility
No
No
No
Volatile
No
Random access
Yes
Yes
Yes
Yes
No
Latency
(access time)
~15 ms
(swift)
~150 ms (moderate)
None (instant)
None (instant)
Lack of random access (very slow)
Controller
Internal
External
Internal
Internal
External
Failure with imminent
data loss
Head crash
Circuitry
Error detection
Diagnostic (
S.M.A.R.T.
Error rate measurement
Indicated by downward spikes in transfer rates
(Short-term storage)
Unknown
Price per space
Low
Low
High
Very high
Very low (but expensive drives)
Price per unit
Moderate
Low
Moderate
High
Moderate (but expensive drives)
Main application
Mid-term archival, routine backups, server, workstation storage expansion
Long-term archival,
hard copy
distribution
Portable electronics; operating system
Real-time
Long-term archival
Media
edit
Semiconductor
edit
Main article:
Semiconductor memory
Semiconductor memory
uses
semiconductor
-based
integrated circuit
(IC) chips to store information. Data are typically stored in
metal–oxide–semiconductor
(MOS)
memory cells
. A semiconductor memory chip may contain millions of memory cells, consisting of tiny
MOS field-effect transistors
(MOSFETs) and/or
MOS capacitors
. Both
volatile
and
non-volatile
forms of semiconductor memory exist, the former using standard MOSFETs and the latter using
floating-gate MOSFETs
In modern computers, primary storage almost exclusively consists of dynamic volatile semiconductor
random-access memory
(RAM), particularly
dynamic random-access memory
(DRAM). Since the turn of the century, a type of non-volatile
floating-gate
semiconductor memory known as
flash memory
has steadily gained share as off-line storage for home computers. Non-volatile semiconductor memory is also used for secondary storage in various advanced electronic devices and specialized computers that are designed for them.
As early as 2006,
notebook
and
desktop computer
manufacturers started using flash-based
solid-state drives
(SSDs) as default configuration options for the secondary storage either in addition to or instead of the more traditional HDD.
35
36
37
38
39
Magnetic
edit
Magnetic storage
uses different patterns of
magnetization
on a
magnetically
coated surface to store information. Magnetic storage is
non-volatile
. The information is accessed using one or more read/write heads which may contain one or more recording transducers. A read/write head only covers a part of the surface so that the head or medium or both must be moved relative to another in order to access data. In modern computers, magnetic storage will take these forms:
Magnetic disk
Floppy disk
, used for off-line storage;
Hard disk drive
, used for secondary storage.
Magnetic tape
, used for tertiary and off-line storage;
Carousel memory
(magnetic rolls).
In early computers, magnetic storage was also used as:
Microcode
storage in
transformer read-only storage
Primary storage in a form of
magnetic memory
, or
core memory
core rope memory
thin-film memory
and/or
twistor memory
Magnetic-tape was often used for secondary storage;
Tertiary (e.g.
NCR CRAM
) or off line storage in the form of magnetic cards.
Magnetic storage does not have a definite limit of rewriting cycles like flash storage and re-writeable optical media, as altering magnetic fields causes no physical wear. Rather, their life span is limited by mechanical parts.
40
41
Optical
edit
Optical storage
, the typical
optical disc
, stores information in deformities on the surface of a circular disc and reads this information by illuminating the surface with a
laser diode
and observing the reflection. Optical disc storage is
non-volatile
. The deformities may be permanent (read only media), formed once (write once media) or reversible (recordable or read/write media). The following forms are in common use as of 2009
[update]
42
CD
CD-ROM
DVD
BD-ROM
: Read only storage, used for mass distribution of digital information (music, video, computer programs);
CD-R
DVD-R
DVD+R
BD-R
: Write once storage, used for tertiary and off-line storage;
CD-RW
DVD-RW
DVD+RW
DVD-RAM
BD-RE
: Slow write, fast read storage, used for tertiary and off-line storage;
Ultra Density Optical
or UDO is similar in capacity to
BD-R or BD-RE
and is slow write, fast read storage used for tertiary and off-line storage.
Magneto-optical disc storage
is optical disc storage where the magnetic state on a
ferromagnetic
surface stores information. The information is read optically and written by combining magnetic and optical methods. Magneto-optical disc storage is
non-volatile
sequential access
, slow write, fast read storage used for tertiary and off-line storage.
3D optical data storage
has also been proposed.
Light induced magnetization melting in magnetic photoconductors has also been proposed for high-speed low-energy consumption magneto-optical storage.
43
Paper
edit
Paper data storage
, typically in the form of
paper tape
or
punched cards
, has long been used to store information for automatic processing, particularly before general-purpose computers existed. Information was recorded by punching holes into the paper or cardboard medium and was read mechanically (or later optically) to determine whether a particular location on the medium was solid or contained a hole.
Barcodes
make it possible for objects that are sold or transported to have some computer-readable information securely attached.
Relatively small amounts of digital data (compared to other digital data storage) may be backed up on paper as a
matrix barcode
for very long-term storage, as the longevity of paper typically exceeds even magnetic data storage.
44
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Other
edit
Vacuum-tube memory:
Williams tube
used a
cathode ray tube
, and a
Selectron tube
used a large
vacuum tube
to store information.
Electro-acoustic memory:
Delay-line memory
used
sound waves
in a substance such as
mercury
to store information.
Optical tape
is a medium for optical storage, generally consisting of a long and narrow strip of plastic, onto which patterns can be written and from which the patterns can be read back.
Phase-change memory
uses different mechanical phases of
phase-change material
to store information in an X–Y addressable matrix and reads the information by observing the varying
electrical resistance
of the material.
Holographic data storage
stores information optically inside
crystals
or
photopolymers
, for example, in HVDs (
Holographic Versatile Discs
). Holographic storage can utilize the whole volume of the storage medium, unlike optical disc storage, which is limited to a small number of surface layers.
Magnetic photoconductors store magnetic information, which can be modified by low-light illumination.
43
Molecular memory
stores information in
polymers
that can store electric charge.
46
DNA
stores digital information in DNA
nucleotides
47
48
49
50
See also
edit
Wikiversity has learning resources about
Computer data storage
Aperture (computer memory)
Mass storage
Memory leak
Memory protection
Page address register
Stable storage
Secondary, tertiary and off-line storage topics
edit
Data deduplication
Data proliferation
Data storage tag
used for capturing research data
Disk utility
File system
Flash memory
Geoplexing
Information repository
Noise-predictive maximum-likelihood detection
Removable media
Spindle
Virtual tape library
Wait state
Write buffer
Write protection
Cold data
Notes
edit
References
edit
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public domain material
from
Federal Standard 1037C
General Services Administration
. Archived from
the original
on 22 January 2022.
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Further reading
edit
Amelia Acker. 2025.
Archiving Machines: From Punch Cards to Platforms
. MIT Press.
Goda, K.; Kitsuregawa, M. (2012).
"The history of storage systems"
Proceedings of the IEEE
100
1433–
1440.
doi
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Memory & storage
, Computer history museum
Basic
computer
components
Input devices
Pointing devices
Graphics tablet
Game controller
Light pen
Mouse
Optical
Optical trackpad
Pointing stick
Touchpad
Touchscreen
Trackball
Other
Keyboard
Image scanner
Graphics card
GPU
Microphone
Refreshable braille display
Sound card
Sound chip
Webcam
Softcam
Output devices
Monitor
Screen
Refreshable braille display
Printer
Plotter
Speakers
Sound card
Graphics card
Removable
data storage
Disk pack
Floppy disk
Optical disc
CD
DVD
Blu-ray
Flash memory
Memory card
USB flash drive
Computer case
Central processing unit
Microprocessor
Motherboard
Memory
RAM
BIOS
Data storage
HDD
SSD
SATA
NVMe
SSHD
Power supply
SMPS
MOSFET
Power MOSFET
VRM
Network interface controller
Fax modem
Expansion card
Ports
Current
Ethernet
USB
Thunderbolt
Analog audio jack
DisplayPort
HDMI
Obsolete
FireWire
(IEEE 1394)
Parallel port
Serial port
Game port
PS/2 port
eSATA
DVI
VGA
Related
History of computing hardware
History of computing hardware (1960s–present)
List of pioneers in computer science
Primary computer data storage
technologies
Volatile memory
Current
DRAM
SDRAM
DDR SDRAM
DDR
LPDDR
HBM
EDO DRAM
RDRAM
XDR DRAM
QDR
eDRAM
Dual-ported RAM
SRAM
1T-SRAM
Experimental
Z-RAM
T-RAM
Historical
Delay-line memory
Selectron tube
Dekatron
Non-volatile memory
Current
RRAM
3D XPoint
EAROM
EEPROM
EPROM
Flash memory
PROM
ROM
Future
FeRAM
MRAM
NRAM
PRAM
SONOS
Historical
Bubble memory
Drum memory
Magnetic-core memory
Twistor memory
Magnetic storage
media
Wire
(1898)
Tape
(1928)
Drum
(1932)
Ferrite core
(1949)
Hard disk
(1956)
Stripe card
(1956)
MICR
(1956)
Thin film
(1962)
CRAM
(1962)
Twistor
(~1968)
Floppy disk
(1969)
Bubble
(~1970)
MRAM
(1995)
Racetrack
(2008)
Optical storage
media
Blu-ray
(2006)
BD-R
(2006)
BD-RE
(2006)
BD-R XL
(2010)
BD-RE XL
(2010)
Professional Disc
(2003)
PDD
(2004)
DVD
(1995)
DVD-R
(1997)
DVD-RW
(1999)
DVD+RW
(2001)
DVD+R
(2002)
DVD+R DL
(2004)
DVD-R DL
(2005)
Compact disc
(1982)
CD-R
(1988)
CD-i
(1991)
CD-RW
(1997)
Discontinued
Microform
(1870)
Optical tape
(20th century)
Optical disc
(20th century)
LaserDisc
(1978)
WORM
(1979)
GD-ROM
(1997)
MIL-CD
(1999)
DataPlay
(2002)
UDO
(2003)
ProData
(2003)
UMD
(2004)
HD DVD
(2006)
Magneto-optic Kerr effect
(1877)
MO disc
(1980s)
MiniDisc
(1992)
MD Data
(1993)
Hi-MD
(2004)
Optical Assist
Laser turntable
(1986)
Floptical
(1991)
Super DLT
(1998)
Paper data storage
media
Antiquity
Writing
on
papyrus
(c. 3000 BCE)
Paper
(105 CE)
Modern
Index card
(1640s)
Punched tape
(mid-1800s)
Punched card
(1880s)
Edge-notched card
(1904)
Optical mark recognition
(1930s)
Barcode
(1948)
Authority control databases
International
GND
National
Czech Republic
Other
Yale LUX
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