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Encyclopedia > Solid state disk

A solid state disk (SSD, also called solid state drive) is a data storage device that uses non-volatile memory such as flash, or volatile memory such as SDRAM, to store data, instead of the spinning platters found in conventional hard disk drives. While not technically "disks" in any sense, these devices are so named because they are typically used as replacements for disk drives in situations where conventional drives are impractical. Wikipedia does not have an article with this exact name. ... This article or section does not cite its references or sources. ... A flash disk , related to a solid state disk and a solid state drive, is a storage device that uses flash RAM chips rather than conventional spinning platters to store data. ... A USB drive, shown with a 24 mm U.S. quarter coin for scale. ... This article or section does not cite its references or sources. ... Many different consumer electronic devices can store data. ... Non-volatile memory, or non-volatile storage, is computer memory that can retain the stored information even when not powered. ... Several SDRAM ICs on a DIMM package. ... Typical hard drives of the mid-1990s. ...

A typical RAM-based SSD.
A typical RAM-based SSD.
A flash SSD in standard 2.5-inch form factor.
A flash SSD in standard 2.5-inch form factor.

SSDs based on volatile memory such as SDRAM and are categorized by fast data access, less than 0.01 milliseconds (over 250 times faster than the fastest hard drives in 2004) and are used primarily to accelerate applications that would otherwise be held back by the latency of disk drives. Image File history File links RamSan-400. ... Image File history File links RamSan-400. ... Image File history File linksMetadata E-disk_2-5_scsi. ... Image File history File linksMetadata E-disk_2-5_scsi. ... Several SDRAM ICs on a DIMM package. ... 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ...


DRAM-based SSDs typically incorporate internal battery and backup disk systems to ensure data persistence. If power is lost for whatever reason, the battery would keep the unit powered long enough to copy all data from random access memory (RAM) to backup disk. Upon the restoration of power, data is copied back from backup disk to RAM and the SSD resumes normal operation. It has been suggested that MF Battery be merged into this article or section. ... Random access memory (usually known by its acronym, RAM) is a type of data store used in computers that allows the stored data to be accessed in any order — that is, at random, not just in sequence. ...


However, most SSD manufacturers use nonvolatile flash memory to create more rugged and compact alternatives to DRAM-based SSDs. These flash memory-based SSDs, also known as flash disks, do not require batteries, allowing makers to replicate standard disk drive form factors (1.8-inch, 2.5-inch, and 3.5-inch). In addition, nonvolatility allows flash SSDs to retain memory even during sudden power outages, ensuring data retrievability. Just like DRAM SSDs, flash SSDs are extremely fast since these devices have no moving parts, eliminating seek time, latency and other electro-mechanical delays inherent in conventional disk drives. A flash disk , related to a solid state disk and a solid state drive, is a storage device that uses flash RAM chips rather than conventional spinning platters to store data. ...


Solid state disks are especially useful on a computer which already has the maximum amount of RAM. For example, some x86 architectures have a 4 GB limit, but this can effectively be extended by putting the swap file on a SSD. These SSD do not provide as fast storage as main RAM because of the bandwidth bottleneck of the bus they connect to, but would still provide a performance increase over placing the swap file on a traditional hard disk drive. x86 or 80x86 is the generic name of a microprocessor architecture first developed and manufactured by Intel. ... A gigabyte (derived from the SI prefix giga-) is a unit of information or computer storage equal to one billion (that is, a thousand million) bytes. ... Virtual memory is intended to help the programmer by taking care of some memory housekeeping duties. ... Design of the Von Neumann machine The Von Neumann architecture is a computer design model that uses a single storage structure to hold both instructions and data. ... In computer architecture, a bus is a subsystem that transfers data or power between computer components inside a computer or between computers and typically is controlled by device driver software. ... Typical hard drives of the mid-1990s. ...


DRAM based SSDs may also work like buffer cache mechanism. When ever a data is written to the memory corresponding block in the memory is marked as dirty block and all dirty blocks can be flushed to the actual hard drive based on following two types. 1. Time (like every 10 seconds, flush all dirty data), 2. Threshold (when the ratio of dirty data to SSD size exceeds some predetermined value, flush the dirty data).

Contents

Advantages and disadvantages of SSDs

Flash based SSDs have several unique advantages:

  • Faster read time – In some cases, twice or more than that of the fastest hard drives.
  • Faster boot time - Result of the faster read time.
  • Lower power consumption - no mechanical parts result in less power consumption.
  • No noise - Lack of mechanical parts makes the SSD completely silent.
  • Better reliability - Lack of mechanical parts result in less wear and tear. In the past, Flash based SSDs were limited in the number of read/write cycles, but modern Flash technology and error correction allow Flash SSDs to operate several years without fail (some manufacturers claim as many as 10 years).

Flash based SSDs also have several disadvantages:

  • Price - As of late 2006 Flash prices are still considerably higher per Gigabyte than those of comparable conventional hard drives (around $25 per GB).
  • Slower write time - Flash has a slower write time than high-end hard drives (around 18 MB/s compared to over 50 MB/s for hard drives), though this varies considerably based on the make and model.
  • Lower reliability - Flash based SSDs have relatively limited read/write cycles compared to hard drives which can last over a decade without mechanical malfunction.
  • Lower recoverability - After mechanical failure the data is completely lost as the cell is destroyed, while if normal HDD suffers mechanical failure the data is often recoverable using expert help.

Typical hard drives of the mid-1990s. ... To meet Wikipedias quality standards, this article may require cleanup. ...

Availability

Currently flash-based SSDs are priced outside the mainstream consumer market and very limited in quantity. SSDs have been appearing in ultra mobile PCs and a few light weight laptop systems, adding a US$200–$800 premium to the systems, depending on the capacity, form factor and transfer speeds. Only a handful of companies offer large (>32 GB) SSD drives with write speeds adequate for replacing traditional drives, but these drives are available in limited quantities, very high priced and available by special request only. The United States dollar is the official currency of the United States. ... GB may stand for: Gb (digraph) GB Airways GB Glace, a Swedish ice cream company ABX Air (IATA airline code GB) Game Boy line Games behind, in sports scores Gigabit (Gb) Gigabyte (GB) Government and binding theory by Noam Chomsky Great Britain Griesedieck Brothers beer Guinea Bissau, a country in...

Samsung Group is one of the largest South Korean business groupings. ... SanDisk Corporation (NASDAQ: SNDK), formerly SunDisk, is an American multinational corporation which designs and markets flash memory card products. ... January 4 is the 4th day of the year in the Gregorian calendar. ... 2007 (MMVII) is a common year starting on Monday of the Gregorian calendar. ... This article is about the history, geography, and people of the island known as Taiwan. ... A-DATA Technology is a Taiwanese computer peripheral company. ... This article is about the city of Las Vegas in Nevada. ... The International Consumer Electronics Show (CES) is a trade show held each January in Las Vegas, Nevada, and is sponsored by the Consumer Electronics Association. ...

External references

  • STORAGEsearch.com SSD portal site
  • 2005 SSD Survey by STORAGEsearch.com
  • Samsung's Solid State Disk Drive Unveiled - Article and an interview with Samsung covering their upcoming commercial Flash SSD.

References

  1. ^ Sandisk press release 4 January 2007.
  2. ^ Future of Flash revealed

  Results from FactBites:
 
Solid state disk - Wikipedia, the free encyclopedia (573 words)
Solid state disk (SSD, also called solid state drive) is a data storage device that uses memory chips, such as SDRAMs, to store data, instead of the spinning platters found in conventional hard disk drives.
The first, SSDs based on fast, volatile memory such as SDRAM, are categorized by extremely fast data access, less than 0.01 milliseconds (over 250 times faster than the fastest hard drives in 2004) and are used primarily to accelerate applications that would otherwise be held back by the latency of disk drives.
To avoid confusion with the first type, these disks are generally referred to as "flash disks." Occasionally, the term is used to include keydrives, since they are technically solid-state and RAM-based.
Solid state - Wikipedia, the free encyclopedia (139 words)
Solid state devices are data storage device components that uses memory chips, such as SDRAMs, to store data.
Solid State Records is a division of Tooth and Nail Records
Solid state (electronics) circuits are circuits that do not contain vacuum tubes or, more currently, no moving parts.
  More results at FactBites »

 
 

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