Write once read many

Last updated

Write once read many (WORM) describes a data storage device in which information, once written, cannot be modified. This write protection affords the assurance that the data cannot be tampered with once it is written to the device, excluding the possibility of data loss from human error, computer bugs, or malware.

Contents

On ordinary (non-WORM) data storage devices, the number of times data can be modified is limited only by the lifespan of the device, as modification involves physical changes that may cause wear to the device. The "read many" aspect is unremarkable, as modern storage devices permit unlimited reading of data once written. [Note 1]

WORM protects the important files by keeping them safe and intact. It ensures the highest level of integrity and data security by eliminating the risk of important data from being deleted or modified. This way, the WORM helps to preserve the authenticity and safety of recorded data.

History

WORM drives preceded the invention of the CD-R, DVD-R and BD-R. An example was the IBM 3363. [1] These drives typically used either a 5.1 in (13 cm) or a 12 in (30 cm) disc in a cartridge, with an ablative optical layer that could be written to only once, and were often used in places like libraries that needed to store large amounts of data. Interfaces to connect these to PCs also existed.

Punched cards and paper tape are obsolete WORM media. Although any unpunched area of the medium could be punched after the first write of the medium, doing so was virtually never useful. Read-only memory (ROM) is also a WORM medium. Such memory may contain the instructions to a computer to read the operating system from another storage device such as a hard disk. The non-technical end-user, however, cannot write the ROM even once but considers it part of the unchangeable computing platform.

WORM was utilized for Broker-dealer records within the Financial Industry Regulatory Authority and the U.S. Securities and Exchange Commission.

Current WORM drives

Once written to, the data on a once-writable optical disc can not be modified and the space is reserved. DVD-R.jpg
Once written to, the data on a once-writable optical disc can not be modified and the space is reserved.

The CD-R, DVD-R and BD-R optical discs for computers are common WORM devices. On these discs, no region of the disc can be recorded a second time. Through packet writing, which uses the Universal Disk Format (UDF) file system, these discs often use a file system that permits additional files, and even revised versions of a file by the same name, to be recorded in a different region of the disc. To the user, the disc appears to allow additions and revisions until all the disk space is used.

The SD card and microSD card spec allows for multiple forms of write-protection. The most common form, only available when using a full-size SD card, provides a physical write protection switch which allows the user to advise the host card reader to disallow write access. This does not protect the data on the card if the card reader hardware is not built to respect the write protection switch. [2]

Multiple vendors beginning in the early 2000s developed Magnetic WORM devices. These archival grade storage devices utilize a variation of RAID and magnetic storage technologies to secure data from unauthorized alteration or modification at both the hardware and software levels. As the cost of magnetic (and solid-state) storage has decreased, so has the cost for these archival storage technologies. These technologies are almost always integrated directly into a content/document management system that manages retention schedules and access controls, along with document level history. [3] [4]

There are multiple vendors providing Magnetic Storage technologies including NetApp, [5] EMC Centera, [6] KOM Networks, [7] and others. In 2013, GreenTec-USA, Inc. developed WORM hard disk drives in capacities of 3 TB and greater. Prevention of rewrite is done at the physical disk level and cannot be modified or overridden by the attached computer. [8] [9]

Research

In recent years[ when? ] there has been a renewed interest in WORM based on organic components, such as PEDOT:PSS [10] [11] or other polymers such as PVK [12] or PCz. [13] Organic WORM devices, considered organic memory, could be used as memory elements for low-power RFID tags. [14]

Notes

  1. ↑ Historical exceptions include time-limited discs such as Flexplay, designed for short-term rental of movies; and early non-volatile memory technologies such as magnetic-core memory and bubble memory, from which reading data also erased it.

See also

Related Research Articles

<span class="mw-page-title-main">Computer data storage</span> Storage of digital data readable by computers

Computer data storage or digital data storage is a technology consisting of computer components and recording media that are used to retain digital data. It is a core function and fundamental component of computers.

<span class="mw-page-title-main">Disk storage</span> General category of storage mechanisms

Disk storage is a data storage mechanism based on a rotating disk. The recording employs various electronic, magnetic, optical, or mechanical changes to the disk's surface layer. A disk drive is a device implementing such a storage mechanism. Notable types are hard disk drives (HDD), containing one or more non-removable rigid platters; the floppy disk drive (FDD) and its removable floppy disk; and various optical disc drives (ODD) and associated optical disc media.

Universal Disk Format (UDF) is an open, vendor-neutral file system for computer data storage for a broad range of media. In practice, it has been most widely used for DVDs and newer optical disc formats, supplanting ISO 9660. Due to its design, it is very well suited to incremental updates on both write-once and re-writable optical media. UDF was developed and maintained by the Optical Storage Technology Association (OSTA).

A direct-access storage device (DASD) is a secondary storage device in which "each physical record has a discrete location and a unique address". The term was coined by IBM to describe devices that allowed random access to data, the main examples being drum memory and hard disk drives. Later, optical disc drives and flash memory units are also classified as DASD.

<span class="mw-page-title-main">SD card</span> Type of memory storage for portable devices

Secure Digital, officially abbreviated as SD, is a proprietary, non-volatile, flash memory card format the SD Association (SDA) developed for use in portable devices.

In computing, a removable media is a data storage media that is designed to be readily inserted and removed from a system. Most early removable media, such as floppy disks and optical discs, require a dedicated read/write device to be installed in the computer, while others, such as USB flash drives, are plug-and-play with all the hardware required to read them built into the device, so only need a driver software to be installed in order to communicate with the device. Some removable media readers/drives are integrated into the computer case, while others are standalone devices that need to be additionally installed or connected.

<span class="mw-page-title-main">Magneto-optical drive</span> Computer drive that uses removable MO media

A magneto-optical drive is a kind of optical disc drive capable of writing and rewriting data upon a magneto-optical disc. 130 mm (5.25 in) and 90 mm (3.5 in) discs were the most common sizes. In 1983, just a year after the introduction of the compact disc, Kees Schouhamer Immink and Joseph Braat presented the first experiments with erasable magneto-optical compact discs during the 73rd AES Convention in Eindhoven. The technology was introduced commercially in 1985. Although optical, they normally appear as hard disk drives to an operating system and can be formatted with any file system. Magneto-optical drives were common in some countries, such as Japan, but have fallen into disuse.

<span class="mw-page-title-main">USB flash drive</span> Data storage device

A flash drive is a data storage device that includes flash memory with an integrated USB interface. A typical USB drive is removable, rewritable, and smaller than an optical disc, and usually weighs less than 30 g (1 oz). Since first offered for sale in late 2000, the storage capacities of USB drives range from 8 to 256 gigabytes (GB), 512 GB and 1 terabyte (TB). As of 2023, 2 TB flash drives were the largest currently in production. Some allow up to 100,000 write/erase cycles, depending on the exact type of memory chip used, and are thought to physically last between 10 and 100 years under normal circumstances.

In information technology, a backup, or data backup is a copy of computer data taken and stored elsewhere so that it may be used to restore the original after a data loss event. The verb form, referring to the process of doing so, is "back up", whereas the noun and adjective form is "backup". Backups can be used to recover data after its loss from data deletion or corruption, or to recover data from an earlier time.  Backups provide a simple form of disaster recovery; however not all backup systems are able to reconstitute a computer system or other complex configuration such as a computer cluster, active directory server, or database server.

Non-volatile memory (NVM) or non-volatile storage is a type of computer memory that can retain stored information even after power is removed. In contrast, volatile memory needs constant power in order to retain data.

Reading is an action performed by computers, to acquire data from a source and place it into their volatile memory for processing. Computers may read information from a variety of sources, such as magnetic storage, the Internet, or audio and video input ports. Reading is one of the core functions of a Turing machine.

Digital permanence addresses the history and development of digital storage techniques, specifically quantifying the expected lifetime of data stored on various digital media and the factors which influence the permanence of digital data. It is often a mix of ensuring the data itself can be retained on a particular form of media and that the technology remains viable. Where possible, as well as describing expected lifetimes, factors affecting data retention will be detailed, including potential technology issues.

An optical jukebox is a robotic data storage device that can automatically load and unload optical discs, such as Compact Disc, DVD, Ultra Density Optical or Blu-ray and can provide terabytes (TB) or petabytes (PB) of tertiary storage. The devices are often called optical disk libraries, "optical storage archives", robotic drives, or autochangers. Jukebox devices may have up to 2,000 slots for disks, and usually have a picking device that traverses the slots and drives. Zerras Inc. provides a removeable capsule that holds up to 200 discs per library which can be scaled-out to manage 1600 discs per 42U rack unit. The arrangement of the slots and picking devices affects performance and maintenance costs, depending on the robotics design, the space between a disk and the picking device. Seek times and transfer rates vary depending upon the optical technology used.

In computing, external storage refers to non-volatile (secondary) data storage outside a computer's own internal hardware, and thus can be readily disconnected and accessed elsewhere. Such storage devices may refer to removable media, compact flash drives, portable storage devices, or network-attached storage. Web-based cloud storage is the latest technology for external storage.

<span class="mw-page-title-main">Optical disc recording technologies</span> List of technologies used to write to optical discs

Optical disc authoring requires a number of different optical disc recorder technologies working in tandem, from the optical disc media to the firmware to the control electronics of the optical disc drive.

<span class="mw-page-title-main">Holographic data storage</span> Data storage technology

Holographic data storage is a potential technology in the area of high-capacity data storage. While magnetic and optical data storage devices rely on individual bits being stored as distinct magnetic or optical changes on the surface of the recording medium, holographic data storage records information throughout the volume of the medium and is capable of recording multiple images in the same area utilizing light at different angles.

<span class="mw-page-title-main">Ultra Density Optical</span> Optical disc designed for the storage of digital video

Ultra Density Optical (UDO) is an optical disc format designed for high-density storage of high-definition video and data. The format was introduced by Sony to replace the Magneto-optical disc format.

<span class="mw-page-title-main">Read-only memory</span> Electronic memory that cannot be changed

Read-only memory (ROM) is a type of non-volatile memory used in computers and other electronic devices. Data stored in ROM cannot be electronically modified after the manufacture of the memory device. Read-only memory is useful for storing software that is rarely changed during the life of the system, also known as firmware. Software applications, such as video games, for programmable devices can be distributed as plug-in cartridges containing ROM.

This glossary of computer hardware terms is a list of definitions of terms and concepts related to computer hardware, i.e. the physical and structural components of computers, architectural issues, and peripheral devices.

Solid-state storage (SSS) is non-volatile computer storage that has no moving parts – uses only electronic circuits. This solid-state design dramatically differs from the commonly-used competing technology of electromechanical magnetic storage which uses moving media coated with magnetic material. Generally, SSS is much faster but more expensive for the same amount of storage.

References

  1. ↑ "IBM 3363 optical WORM drive". November 21, 1987 – via Computer History Museum Archive.
  2. ↑ "Simplified Specifications - SD Association, version 3.10 , Part 1, Physical Layer, section 4.3.6" Write Protect Management"". www.sdcard.org. Retrieved 2019-04-11.
  3. ↑ http://www.aiim.org/documents/standards/ARP1-2009.pdf [ dead link ]
  4. ↑ "Analysis, Selection, and Implementation of Electronic Document Management Systems (EDMS)" (PDF). Association for Information and Image Management. 2009. Archived (PDF) from the original on 2009-12-29.
  5. ↑ "SnapLock: WORM Compliance – Data Compliance". NetApp.
  6. ↑ EMC Centers emc.com
  7. ↑ "Products Overview". Archived from the original on 2012-02-17.
  8. ↑ "GreenTec-USA, Inc. WORM Read Only Disk Drives" http://www.greentec-usa.com
  9. ↑ "Best Practices to Secure Data from Modification: Eliminating the Risk to Online Content" http://greentec-usa.com/wp/GreenTec-WORM-Whitepaper.pdf
  10. ↑ Möller, Sven; Perlov, Craig; Jackson, Warren; Taussig, Carl; Forrest, Stephen R. (2003). "A polymer/Semiconductor write-once read-many-times memory". Nature. 426 (6963): 166–169. Bibcode:2003Natur.426..166M. doi:10.1038/nature02070. PMID   14614502. S2CID   4337352.
  11. ↑ "Smith and Forrest "A low switching voltage organic-on-inorganic heterojunction memory element utilizing a conductive polymer fuse on a doped silicon substrate"".
  12. ↑ "Lin and Ma "Realization of write-once-read-many-times memory devices based on poly(N-vinylcarbazole) by thermally annealing"".
  13. ↑ Teo, E. Y. H.; Zhang, C.; Lim, S. L.; Kang, E.; Chan, D. S. H.; Zhu, C. (May 2009). "An Organic-Based Diode–Memory Device With Rectifying Property for Crossbar Memory Array Applications". IEEE Electron Device Letters . 30 (5): 487–489. Bibcode:2009IEDL...30..487Y. doi:10.1109/LED.2009.2017387. ISSN   0741-3106. S2CID   19858062.
  14. ↑ "Holst Centre reports major step towards organic RFID"
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.